In other words, why does existence exist? I think it has something to do with the fact that nonexistence is something that does not exist, so things can't be like that. The only alternative is existence. If nothing existed, that would be reality, and reality would not be what it is because nonexistence cannot exist. But what made that the case?

Any hypothetical cause of existence would be a form of existence, so it could not really be a cause of existence. So, apparently, existence cannot have a cause. Does that mean cause is not the metaphysical requirement we think it is?

What is the explanation here?