Especially when we have evidence that more complex things can arise from less complex things without a supernatural manager guiding the process.

This isn't being questioned. I'm asking about origins.

What makes you look at the vast set of "somethings" that might have been responsible for the origin of the universe, and choose exactly the same thing that our ancestors considered a good explanation for the origins of thunder (and now we know they were wrong)?

I don't consider it a good explanation. But others have. And I don't see why it's necessarily bad. So far, I've seen no reason on this thread to update and make deism an awful explanation.