I know it's a few days later now. But I'm agnostic and not explicitly atheist and the reason is that, one of the few scenarios that made sense to me, I never thought of as simulation theory.
It was that the big bang doesn't remove the possibility of a God. That God could just be an alien that exists outside our concept of time and created this universe with the concept of time as an experiment.
I suppose this could be a simulation too. That is, that alien outside our concept of time creates a simulation of a universe with a linear time.