To elaborate, if God exists then consciousness depends on having an immaterial soul. If consciousness depends on an immaterial soul, then simulated entities can never truly be conscious. If the simulated entities aren't really conscious they are incapable of suffering, and there's no reason for God to intervene in the simulation.
The thought experiment is not a very effective argument against theism, as it assumes non-existence of souls, but it serves the purpose of illustrating how unthinkably horrible things can actually happen.
Many theists deny this...
To elaborate, if God exists then consciousness depends on having an immaterial soul. If consciousness depends on an immaterial soul, then simulated entities can never truly be conscious. If the simulated entities aren't really conscious they are incapable of suffering, and there's no reason for God to intervene in the simulation.
The thought experiment is not a very effective argument against theism, as it assumes non-existence of souls, but it serves the purpose of illustrating how unthinkably horrible things can actually happen.