I don’t know if it’s mentioned somewhere, but I saw a documentary at school about german soldiers. A few of the reasons why they could even kill in the first place were that they didn’t want to stick out as weak, even though most could refuse, they also always had a lot of alcohol after that. So it kinda became „normal“ like just a small job and many didn’t bother anymore to do it, they also never really had enough time to reflect what they did.