It’s basically a play on simulation theory.

The idea is that we are all just coded into a simulation and everything around us is fake but since we’re built into the system there’s genuinely no way to prove that right or wrong.

In the case of this comic, a bunch of people in the simulation manage to see proof of it being an actual simulation for the first time when they see someone manage to leave it… As a result they want to get out as well and fail their own attempts.