Imagine if the current crop of well known holy men would write their own book and it be added to the bible. Can you imagine how awful, self serving, and corrupted that would be?
Why should we think anything else happened 300-500 years after Jesus died? Everyone likes to say history repeats itself, history rhymes, etc. Why wouldn't we think that those in power, or prominence, at that time would have better "truth" than some corrupt bad person who collects checks preaching about how you're going to hell, all the while watching his wife get piped by the pool guy?