It needs be kept in mind that before Christianity, the rulers for hundreds of years were the Romans. Their empire and their power was extensive. The Romans had their own religion, their own gods and, no doubt, their own heirarchy of religious leaders. When it became apparent that the Christians could not be 'put down' (Though Nero and others tried) it was always a matter of "If we can't beat 'em, we'll join 'em." However, we'd better get in there and write up the Rule Book the way we want it. We've still got the power to do that...and so they did. And as it all happened hundreds of years after the death of Jesus Christ, I leave it to your imagination as to how much of what is purported to have been said and done by JC is actually true,
This is not to disparage one of the world greatest and influential teachers. But, to my mind, Jesus of Nazareth was just one of the many spiritual teachers who has trodden on Mother Earth. I expect there are others among us even now.
From the accounts I heard, the Bible was revamped to exclude anything that smacked of a lot of earlier beliefs, such as Reincarnation. Then came all this business about 'The Only Son of God,' The invention of hell fire and brimstone for the non-believers and those who would not 'repent' et cetera. Such fear-tactic teachings still hold many in this grip of fear.
Those who control are very, very reluctant to relinquish control, be that political or religious power. But it certainly seems that when the Bible was compiled to read much as it does today, it was done so by persons who wished to hold on to the power they had at that time.