Why do people believe the Bible?

I’ve read most of the Old Testament, and I’m just starting on the New for the first time. Now, as far as history goes, the New Testament was okayed and published by the Church about 300 years AD (and many other sources say that AD was different as well, that Christ lived and wasn’t a god or his true son).

Let me clarify. This question isn’t about dogma or karma, or whether people believe or disbelieve. If you look closely it is about WHY one believes. I would say I believe in God because it helps me pray for the things I wish to manifest in my life. But, I believe in Jesus Christ because he was a leader of the people, and also that Christ does not mean specifically one person in history. There have been many in history, in most countries, in much of the world we know and study that have embodied “Christ”.
So, would you please keep your answers towards WHY you believe in the bible, or WHY don’t you. I don’t really care whether you believe it’s true.