Though I do wonder if things would be even worse if those people didn’t have religion claiming there’s external punishment or reward if they control themselves a bit.

Though when Christianity tried to resolve the “if I cross the line into eternal damnation then I might as well do whatever I want after that” problem by saying they can repent, it opened up a “do whatever you want and then repent” loophole, so it could do as much to make people think they can get away with shit, especially when combined with a strong belief that the afterlife will be better.

Also, I think the shitiness is ingrained deep in our species, hell in most species. The reality is that strategic betrayal has always been the optimal solution to the prisoner dilemma, and while real world versions of it continue after that betrayal, I’d bet a high portion of historic animal ones involved the one intending to be nice or trusting not surviving, so I’d guess that survival of the fittest has a bias towards opportunistic assholes.