I've always wondered that about the Bible. What if a couple of random ass dudes were hanging around, talking about something to do...
"Hey, you know what would be hilarious? Let's write a book with all these crazy ass, magical stories about some guy who is the son of a god, but let's make it seem kind of realistic by saying that it's a collection of stories from 'witnesses' so people actually think it's REAL!!! HAHAHA, oh shit, this is gonna be HILARIOUS!!!"
It would have to be a pretty large conspiracy. The writtings of The Bible were written by quite a number of people over a long period of time.