Why is this revelation unknown? Let us summarize the common errors and false teachings which are taught in Christian Churches, which will demonstrate the need to establish a New Church:
God is One, One Divine Being. He is not three divine beings
There is a Trinity: the Divine Itself, the Divine Human, and the Divine Proceeding
The mystery of the Trinity was revealed: it is not three divine beings, it is a Divine procession. God Himself is so big, so infinite, and so beyond us that He cannot be approached directly by humans. This is the Divine Itself. In order to become manifest to our human minds, He appears in human form. This is the Divine Human. Scripture states that Jesus is the image of the unseen God. From the Divine Human the Divine spirit proceeds and influences all of humanity: this is the Divine Proceeding, or Holy Spirit. Thomas Aquinas spoke of the Divine Procession, unfortunately his theology was still trapped by the idea of three divine beings. As a positive development, Oneness Pentecostals have a similar doctrine, although it was developed independently from the revelation given to Swedenborg.
The Son of God was born in time, not from eternity
This is another big error of the Christian Church. The Son of God was the human born in time to the virgin Mary. There is no such thing as a Son of God born from eternity - this is a belief that was added in the Nicene Creed. Yes, Jesus did pre-exist as Jehovah, because He is Jehovah Himself. There is no such thing as a "second" person who then descends and becomes incarnate. In Him there was a Trinity of soul, body, and operation: this was the physical manifestation of the Divine, the Divine Human, and Divine Proceeding. As Paul stated, the fullness of the Godhead resides in Jesus bodily.
The Human born in time was made Divine
This is a truth that became lost once the Christian Church declared the existence of three divine beings. Jesus, once born, had to fight against evil and temptations which he inherited in the external human body from the virgin Mary. The minute He was born, there was a full blown war between Heaven and Hell: Jehovah began to fight directly against all of Hell, as they attempted to get Him to commit a sin. He gradually progressed in human growth, until the Human itself was made Divine at the resurrection. Most modern churches still divide the Divine and human natures of Jesus. The Catholic Church, in order to claim that their Pope is the Vicar of Christ, will stress the two separate natures. In fact, they helped invent this doctrine. This theology is known as "Chaldedonian." Because of Chalcedonian theology, most of the original Christians of the Middle East were declared heretics! Some of this truth is expressed in the mysteries of the Orthodox faith.
As a corollary, it is false to believe that Jesus was just a prophet or a good teacher. This is an outward appearance. Nor was he just an avatar or incarnate angelic being. There is more than just a prophet here. He is the Divine made manifest in human form. Read the Gospels, and understand the claims Jesus made about Himself.
No Sins were Transferred to Jesus on the Cross
The crucifixtion was the last temptation of Jesus, before His Human was made Divine. In common Christian theology, it is believed that sins are somehow automatically transferred onto Jesus on the cross. This is also known as "vicarious atonement." Many believe in instantaneous salvation by just uttering lip confession, and everything is said and done. This is not only a false belief, it has some very bad consequences: people begin not to take responsibility for their actions. It is especially apparent among those who stress that salvation comes by faith alone. The sins that Jesus suffered are the sins He inherited in the human body from the virgin Mary. And, this was all of sin, all of evil. For as His love of humanity was infinite, so the hatred and evil of hell increased against Him as he continued to defeat evil.
There are many passages in scripture that mention the "blood" of Jesus. The bread and wine of the Eucharist are symbolic of His body and blood, and when He made His Human Divine He became the human form of Divine love and truth. "Blood" is symbolic of the Divine truth. It is truth which sanctifies a person: we act according to the truth that we know. That "blood" has this symbolic significance as referring to truth itself, requires an understanding of the spiritual sense of scripture.
Salvation is through Jesus, by Repentance
One must repent, or turn away, from their own sins and pride in order to begin the process of salvation. Sins that one turns away from and held in aversion are the sins that become removed. Repentance involves self-examination. One must do this as if from himself or herself, but acknowledge that only Jesus, the Divine Human can accomplish this through the Holy Spirit. As Jesus conquered all of Hell, and became Divine, the Divine proceeded from Him as the Holy Spirit. This Holy Spirit begins to dwell in your heart as you acknowledge your sins, and turn away from them.
How is repentance dependent on what Jesus did? Human free will has a spiritual origin, it comes from a balance between heaven and hell. In our inner psychology, this balance appears as the choice between good and evil. This is communicated by angels or evil spirits. By the time Jesus came, this balance was broken, hell had gained ascendancy and power over mankind, and even the lower angels. That is why God chose to become incarnate: to reorder heaven and hell, and provide a direct link between God and humankind.
There is no Faith Separate from Works or Good Deeds
This is the error of the Protestants: faith is stated to be belief only. This comes from a misinterpretation of the writings of Paul, where he spoke against the "works of the law." However what Paul was talking about was not about good deeds in general, but about the ritualistic ceremonies of the Mosaic law for the Jews. These were symbolic rituals, which no longer were necessary once they became fulfilled in the Christian revelation. One must love God with all their heard, mind, body and will. Unfortunately for Protestant theology, it believes that the humans are passive subjects. No, you must submit your will to God. You must serve not just in thought but in actions according to your thought. There are many passages in scripture which talk about how one must hear and do, hear and obey. Those who listen to the words of God, and do not do them, are foolish. Read Matthew 25, which speaks of doing good deeds to others. Read the book of James. Unfortunately, this theology, as it is taught to people from a young age, gives them a bias where they pass over these commandments and teachings with a blind eye. On this point, the Catholic Church is right.
There is an Afterlife of Heaven and Hell
There is life after death. We will rise in a new spiritual body. When this occurs the thoughts of our mind, our innermost nature, is completely revealed. Nothing remains hidden. Not only that, external restraints on our actions are removed. We will go to the place that matches our innermost nature: this will be either heaven or hell. In addition to heaven and hell, there is a spiritual world between the two which all who die enter immediately after death. In many cases, souls who have died who enter this region are not prepared for judgment. Thus periodically souls are judged and arranged en masse, where they are judged all at once. This occurs when the equilibrium between heaven and hell become imbalanced: it is known as the Last or Final Judgment. This occurs in the spiritual world, not here on earth. There is no such thing as the end of the world. There is such a thing as the end of a world age, where the old faith dies and new faith is born anew.
There is a Hidden Spiritual Sense in Scripture
Fundamentalists tend to be stuck at the literal meaning of scripture. While there is a literal sense to scripture, scripture has multiple levels of meaning. Scripture was written through a series of symbolic correspondences, where the literal words are symbolic of higher spiritual ideas. And this is the subject matter of most of the revelation given to Swedenborg: it is to show how and why scripture is Divinely inspired, how it is different from other books written. Word by word, verse by verse, Swedenborg spent many years to prove and reveal how scripture is Divinely Inspired - most of it is in his massive work, Heavenly Arcana, also known as Arcana Coelestia. It means "heavenly secrets." And it is beautiful for those who are willing to open their minds: because these are eternal spiritual truths, with immediate application to one's life. Sort of like the writing and poetry of the Sufi mystic Rumi. When scripture is read, there is inner communication with the angels of heaven, although we are not aware of it. This revelation of the inner meaning of scripture is the Second Coming. In the First Coming, the Word of God was revealed in human flesh. In the Second Coming, the Word of God is now revealed in the Bible. It is available to all, who seek to learn of the revelation.
There will be Opposition between the Old Churches and the New
Given the points I just said, is the old faith of Christianity compatible with the new one? No. Unfortunately over the centuries, much of traditional Christianity has become corrupted. Which explains why many have left it. There are, however, exceptions, some churches are more open minded than others. Scripture states, when Jesus comes, will He find faith on this earth? It means when the Christian Church has become so corrupt, a new revelation will be made to reveal the truth. You will either embrace it, or hate it. So, from the religious leaders of the old faith, there will be intense opposition. And censorship. This is the reason why Emanuel Swedenborg is so unknown. He made no attempt to establish a church, and wrote most of his works anonymously. This Church, unlike the ones before it, will be established by the Lord alone through his angels, in a hidden way. As the New Church of the New Jerusalem descends from heaven, from this heavenly revelation, the opposition of the older churches will be so intense it will lead to a lot of religious debate: this is known as the spiritual battle of Armageddon. The truth that descends is portrayed in the book of Revelation as the White Horse that descends from heaven. Once the truth is known, one can effectively fight against what is false. The old cannot be mixed with the new: no one puts a patch of unshrunk cloth on an old garment; for the patch pulls away from the garment, and a worse tear results. Nor do people put new wine into old wineskins; otherwise the wineskins burst, and the wine pours out and the wineskins are ruined; but they put new wine into fresh wineskins, and both are preserved. (Matt. 9:16-17)
What to do?
First, learn the doctrines of the New Church. Learn the differences with the old way of thinking. Reject what is false, share with others. Change first comes with learning, then through doing. Do what the original Christians did: establish a home church at home. This is how the Christian church began, this is how the new one will begin as well. Good luck, and God be with you.