Is this a real question? It's a good one though, and I can explain. I'll try to keep it short.
The problem is that when people don't believe in God, they don't have all the right info for it to make sense. It starts with our fall from grace. When Adam and Eve sinned, it corrupted them, and all their descendants.
Satan exploited a basic human trait of innocence and trusting, and turned people away from God by confusing them with false knowledge. By doing this, he succeeded in taking over the world and controlling people at their weakest points in their mentality. Then, he did whatever he could to hide himself, so people wouldn't pin the blame on him.
As a Christian, it is my goal to reveal these things to the world, not to "win points for God" as is commonly misconceived, but to save people from themselves and the demonic situation at hand. Eventually, our mortal human bodies will completely disintegrate, but our souls remain forever, and to still be sinning and unrepentant means we destroy our own souls.