One way to look at the Bible is that it is nothing more than a chronolog of man's development into conscious thought (of course, most of Genesis is myth). This runs through the whole Bible, old testament and new. The New Testament, as well as Jesus' ministry, was merely an attempt to speed the process up. The apostles were bicameral at the outset, and Jesus offered the gift of conscious thought. He used parables to facilitate this process.
Now, Paul comes along and misinterprets it all. He errantly takes it literally, and starts writing as if the Bible was meant for use as a guide book. This was an errant viewpoint, but an innocent error. He was trying to help out, but took the wrong approach. Now, something like 300 years later, St Augustine starts a cult that would be known as the Catholic Church. He picks the books out of all that is available that will support this new cult, and discards everything else. That is where we get the 66 books of the Bible today. And that leads down into the Dark Ages, where the masses do not get to see the whole Bible, or even the part that was selected.
Sometime after the Renaissance, King James sets out to make the Bible public. He has access only to the 66 books that the Catholic church preserved. All the original errors are preserved faithfully, as well as a few transcription errors (you are always going to have those). But even so, this is enough to set off independent Bible study groups. The Protestant denominations come from these. As Paul's innocent errors and the omissions of many of the Gnostic texts are still there, the religions are still not perfect. But it does undermine the stranglehold the Catholic church had, forcing them to become more mainstream.
Now, we reach 1840. About this time, someone independently studies the Bible, but with the purpose of exploiting it to control masses of people and swindle them of their money. This becomes a cult that will eventually spawn the Mormons, the Adventists, the Millennial Dawnists, and Jehovah's Witlesses. This person is not doing this to reach the roots of truth, but to exploit people. Of course, the person doing this claims to be searching for the truth at the roots. And, so does each of the splinter cults that come from this.
Anyone viewing the Bible in this sense is bound to see why all the religions have such mysticism and make little sense. The Catholic teachings do not seem to make sense because of Paul mistakenly taking the Bible literally and St Augustine's efforts to use it to manipulate people. Protestant denominations vary because they started from independent truth-seekers with slightly different viewpoints. And the cults like Jehovah's Witlesses and Mormons started because of a scam where the founders studied independently with nefarious purposes. Hopefully, that will shatter a few myths and help people to understand what exactly the Trinity means.
