Why Are There Natural Explanations For Everything?

Perhaps you Christians can suggest reasons why a God like yours created the universe and man in such a way that there are natural explanations for why we exist, how we think, who we are, and why we behave as we do. As far as I know there are natural explanations for everything you claim a supernatural deity did. You don't think these explanations are good ones, okay, but they exist and they persuade many if not most scientists working in those fields.

Why then is it that your God created this world as he did and revealed himself as he has done that are indistinguishable from him not creating the universe or revealing himself at all? This is what I want to know. In fact, why does reasonable nonbelief exist at all?