I don't see how the opposite is possible. How would a theist believe we are in a simulation? Why would someone make a simulation work seemingly fully rationally and according to very specific laws, only to add a deity or some other supernatural element in it? Would that being even be considered a deity then, if the simulation was created by someone else outside it?

^^ Its functionally similar to theism in a god of gaps sense. Reality was created by a supra-natural (ante this reality) being. The being has omnipotency and omniscience relative to us. Whether theist or nontheist the same additional, nonfalsifiable claim of something beyond universe results. It makes all sorts of assumptions about the supra-world and ultimately just moves all of the problems of our universal origins up one level. It's a more complicated system than even theism.... so not sure why it has so much appeal.

To OP, if you think the meta universe wasn't created supernaturally, then you can reconcile the two.

Atheist here!

Elon Musk should come out as trans-deist already so the term atheism isn't slathered by this kind of silliness (atheism is such a tortured non-tradition as it is). Not that Elon is all bad, and isn't the goose responsible for laying this particular bad egg, but he is popularizing some very silly ideas of late (including this one)...

Of course, simulation theory, such as it is, is probably stupid. The universe in some ways resembles our computational simulations, which are created in the universe and modeled after the universe. Surprise surprise? Self-simulating prophecy?

Do thespians wonder if it's all one big production? Do composers wonder if it's a song-like symphony? To an explorer it's a journey, to a runner it's a race. To the pious it's a test and to the rebels a cause.

What might philosophers with a background in physics, computational modeling, computer science, and anthropology/artificial intelligence wonder it all to be? Hmmm....

I'm forced to presume that things are determined akin to the machinations of a simulation, but all this other stuff about where it comes from, nested simulations, statistical bull-plop, is presumptive nonsense:

It's possible that an egg-laying dragon creates egg-like universes, and since egg universes can internally give rise to multiple universe-egg-laying dragons, there are nearly infinite universal eggs out there in a complex network of what we might call a Russian-nesting-dragon-egg-multiverse. Since there are nearly infinite dragon-egg-universes, statistically we exist in one of them, and naturally we must pay it forward by finding, assisting, or creating new universe-egg-laying dragons to continue the thermodynamically rebellious cycle.

I guess when one eschews the god-assumption one is then free to pick from an infinitely wide range of alternative assumptions... To each their own I guess...

Malebranche is known for his occasionalism, that is, his doctrine that God is the only causal agent, and that creatures merely provide the “occasion” for divine action. On the old textbook account, occasionalism was an ad hoc response to the purported problem in Descartes of how substances as distinct in nature as mind and body are can causally interact. According to this account, Malebranche was driven by this problem with Cartesian dualism to propose that it is God who brings it about that our sensations and volitions are correlated with motions in our body.

SEP