The problem with theistic hypotheses is that they start from the idea that a humanoid god is a simple explanation (since our brains devote a lot of effort to understanding humans, so humans seem misleadingly simple). The simulation hypothesis treats the idea of an intelligent entity running a simulation as a starting point, and the details of how such an entity would come to exist are taken as a serious point that needs to be explained, whereas with god hypotheses the matter of how that god exists in the first place is generally just waved away.