Have to? This is bizarre. The universe exists but doesn’t ‘have to.’ We are a product of what occurs in the universe but certainly don’t ‘have to’ be a part of that process. There is no "have to’ in anything I can think of.
You would have to demonstrate a cause was "necessary.’ You would need to demonstrate your first necessary cause was not natural. Before you can postulate a god did it, you have to demonstrate god is a possibility., (You are working backward.) We all agree everything is here, you don’t get to simply assert a god did it. Why would you call a naturally occurring universe God?
Well, so far, you are not off to a good start. Would you like to try again? You have no justification for calling the origin of a universe, “God caused.” I can use the same argument to assert “Blue Universe Creating Bunny caused” Where is this god thing you speak of. You must demonstrate it exists and that it is a possible cause., All your work is before you.
From what I have seen so far… You are wrong.