Theism and atheism fundamentally diverge around the existence of gods. Nothing about atheism assumes that reality had to exist. It certainly exists now, at least.

This is fundamentally incorrect:

There is no pluralism in some strains of theism. So this idea is incorrect. If atheism does not assume reality, it must provide a reason for it to exist. Otherwise, simply saying "well it exists now" is not how logic works. All arguments are anchored in assumptions which must be asserted. There is no escaping this.

I'll give you the benefit of the doubt that you must be new here. I don't know what brought reality about, or if that question even has an answer. If you want to assume that the question requires an answer, and that answer is your god, then have at it.

I will assume you are new here too. Whether or not you accept your premise, the fact remains. Your stating that reality does not need a reason to exist, IS your assumption.