If we can take a look at current or "base reality", all sorts of simulations are present in our daily lives, VR, movies, video games, etc.
With current advancements in technology and AI, we can extrapolate 100, 1000 or even 1,000,000 years and basically assume that post-humans will eventually reach such advancements in technology thanks to exponential developments in AI that will not only allow them to run infinite simulations but basically run them, re-run them with variations, go backwards in time and so on.

Statistically speaking, what are the chances that this is the case? Personally, I find it hard to believe that humans wont have the technology in 500 or even a 100 years and if they do get there (which everything seems to be pointing that way) theres is NOT A CHANCE that we are not in some sort of simulated reality right now