Ah, so cosmic politicians from both sides came along. Got it.
Jokes aside, you still haven't presented any explanation on what made it expand. To my knowledge (unless you can provide a satisfactory argument contrary to this), there is some kind of force that had to set it all into motion.
Now, what could this force be? Could it be another universe? Well, that's a possibility, but how would they collide? From what I understand, gravity works very different when all matter is condensed in one infinitely small place.
Could it be coming from inside? Well, it would be very hard for this to happen, considering how condensed everything is. I don't think so.
So, what could it be? Well, I think it's very possible that this was caused by God. I'm not trying to prove my God, I do not yet have the knowledge on how to do that. But until we have more knowledge, the most likely conclusion is that this was caused by something supernatural. Call it God, call it whatever you want. It's outside our per view at the moment.