One of the surprising things about human nature is the ability to rationalize all behavior - even the most immoral. Everyone fundamentally thinks they're a good person regardless of what they've done, which means they've convinced themselves there are good reasons for what they've done.
I imagine when working in the ethereum ecosystem one says to oneself:
  1. Everyone else is doing it
  2. My users understand all the risks but took them anyway. It's not my fault they assessed the risk wrong.
  3. I'm making money because I'm providing value. It's signal that what I'm doing is the right thing.
This interview with a famous cybercriminal Brett Johnson on Lex Fridman's show is illuminating: https://www.youtube.com/watch?v=cC1LFC0KFSw. He didn't care about his victims because he convinced himself he was doing it for his family - which in his mind washed away the harm it caused and still made him good.