The eternal regress is the greatest enemy of those who proffer simplistic explanations. The eternal regress is the reason

why it doesn’t work to say that there is a little person in the brain (without accounting for that little person). It is the reason why it doesn’t work to announce that everything has to have a cause and then to explain the existence of the universe by reference to “God” without explaining how God came to exist.

The lurking eternal regress is also why no simple explanation is complete.   As Carl Sagan once said: “If you want to make an apple pie from scratch, you must first create the universe.”