So why not always a universe? That's the simpler thing to assume. That's the question you dodged from his video and you dodge again right here in this post. And please don't pull that "god is the universe" thing, because words have meanings and those two words don't mean the same thing. Inserting a god only raises many many more questions. Its answers nothing.
You give yourself a little too much credit when you assume that there must always have been existence. See, to even frame that question you're assuming that time is continuous. But the big bang shaped spacetime. Spacetime formed and evolved throughout the big bang. As you look backward approaching the big bang, our understanding of physics gets stretched significantly, to the point where we have trouble even tracking what spacetime is anymore. So asking what came before the big bang is a fairly nonsensical question. It's at least nonsensical in terms of our everyday understanding of time.
To really understand the universe, you need to understand that time is a part of it. It's not something that exists outside the universe for the universe to exist in. It is molded and shaped, along with space, in lots of ways. In the presence of gravity, and in light of quantum entanglement, in terms of probability. So when you understand that time is a part of the universe, asking what came before the universe is like asking where the universe was before the universe existed.
Asking when something occurred is very much linked with asking where something occurred. What you're asking is like asking where the big bang happened.... the only where we know of, or understand, is inside the universe. The universe occurred everywhere, and nowhere. And the universe occurred forever, and never.
