But if everything needs an explanation, what about God?

Yeah, that's a common question.

The short answer is that no matter what caused the universe, for the universe to exist, there has to be something that wasn't caused or made. This actually fits with the idea of God, who is a self-existent being.

We actually have a whole other set of answers on that topic, so if you want to learn more you can follow this link: If God made everything, who made God?