And they had that Council of Nicea or whatever it was called where a bunch of folks with different agendas decided what was in the Bible and not in the Bible. Like the Book of Enoch, for instance. Enoch was mentioned in the Bible in other places. According to Zechariah Sitchin, Enochs book mentions all these "Watchers" who could easily have been interpreted as people not of this Earth. That would've been incompatible with the rest. There were other books that indicated Jesus endorsed reincarnation. That wasn't compatible with the rest either.

@david75090 there were two councils of Nicea and the council of Ancara.
But that was just the start, the cannon was altered when the Marcionites were incorporated in to the RC and brought with them the Epistles of Paul, before this when the orthodox and the catholics churches schismed they both altered the cannon. The Coptic Christians had a different cannon as did the Ethiopian church and during the reformation the Anglicans cut out 15 books and added in two.
Time and again the cannon of the babble has changed and every denomination claims to have the right one and refuse to believe the others exist.