the simulacrants wouldn't realize the simulation is ever not running.
Kurzgesagt made a video about how in a dying universe (from heat death) civilizations that uploaded their consciousness into a simulation could live forever, by intermittently running the simulation and pausing it for greater and greater amounts of time as expendable energy in the universe diminishes. The consciousness would not perceive the time the simulation isn't running and to them things just go on and on for eternity.
Who would've thought that astronomy as a science only had like 500 years window to the clear sky... That any advanced enough civilization would as quickly and enthusiastically blot out their own skies for short term gains...
VSC and CVS are anagrams of each other after all