Rather than discrete simulation, I'd postulated that they've sort of mechanised the universe. Disciple of the dog spoiler: Somewhat like the earth at (one of) the end(s) of Disciple of the dog, with the world turned into a big machine.
Here, the universe, by some method, is turned into a big machine. Not a discreet simulation, as you are turning something which was just there into the simulation you want, but kind of like a simulation. One overlaid over reality itself. A sort of universe rewriting nuke.