What do you mean? We know quite well how electromagnetism arises from U(1) symmetry in gauge theory. What else is there to know?
So the cause or dare I say reason for the universe being the way it is will depend on its cause.
"The universe" cannot be that cause, as the universe and everything in it is contingent.
But the universe is contingent. It isn't necessary. It is one big chain of dependence.