Narkissos
What you say makes sense, although I have not studied enough, intuitively that seems right from what I have read.
The more history I read, the more I come to realise that there have always been innumerable religious beliefs and practices, even within Judaism and Christianity.
Even in Jesus day, it was not a simple matter that Christ was a Jew. This does not tell us much about him after all. Is there any evidence that he leaned towards any particular sect. Or did he start his own, perhaps he called it Jehovah's Witnesses but the reference was removed by later copyists, just so Joseph Rutherford could come along later and take all the glory.
It would be wonderful and simple, if there were one true and pure religion in the past, and one true religion today. Some try to believe tis is indeed the case, and so avoid history - they find it less painful to carry on dreaming.