If I tell you a story and ask you to keep it safe and tell the people of the world, how long would it be before that story was changed by the people you told it to? a word added here and there, a passage or two removed because they didn't fit in with what someone else thought of the story.
We are Human and we have many weaknesses two of them are not having amazing memories and not being very trustworthy when it comes to the power over people that religion can provide.
Combine the two and you get multiple religious beliefs and armies of people that will kill over them.