"How do you sleep at night?"
"On a bed made of money."
(I'm talking extreme end here, btw). Someone doesn't turn to high crimes overnight nor are they (usually) born that way. You start of making smaller immoral decisions which then become normal. You essentially move the bar a little more and more. People sleep at night frankly because they no longer think that these things are immoral. That's why there's plenty of sayings along the lines of "the path to heaven is long and narrow and the path to hell is short and wide".
Obviously morals are flexible and need to be to survive in this world. But the thing is when people are put into environments that encourage this bar to be pushed too far (by what society determines is too far).
Btw, if you like podcasts Hidden Brain did an episode on this concept that went through how an athlete went from taking no sports enhancing drugs to being a major dealer. And they decompose each step and how reasonable they seem in the context.
Tldr: it's no longer immoral for them, so the real question is "what keeps them up at night?"
Basically the story I remember is that there was a sports athlete that was in the lower ranks and then got a prescription, that they actually needed, that also improved their performance. Then I think it got banned? So they start buying it from another country like China or something. They then started buying in bulk because it was cheaper. Their friends started asking for some because he was getting it for cheap and he didn't think anything of it because he was just helping them save money too. They're his friends after all and he was already buying the stuff. So what difference did it make if he just ordered a little more? Then it started being friends of friends. Before he knew it he was selling tons of this stuff and to people he had no real previous knowledge of.
I now really want to listen to it again so if someone can help find it let me know. I think they might have also talked about Lance (I'm not sure if they interviewed him or that's another podcast I'm thinking of).
Nobody in their fourties who has the life experience of being married with kids is going to work lots of overtime and put up with their boss acting like a child and treating them like they are nobody. I guess that's why they like hiring college grads (that and they don't know their value so can be paid much less).