I have one major issue with what you’re saying—- that who says that they in particular were meant to be the vehicle for our punishment?
There were plenty of Germans who weren’t anti-Semites, and plenty of anti-Semites who weren’t (and aren’t) Germans. And while I don’t know how bechirah works as far as non-Jews go, if it’s like with Jews, then they could have chosen not to. It may have taken more effort, the environment may have added pressure, but nobody was manipulating their brains.
This is from the Jewish perspective of bechirah though. I don’t know how it works with non-Jews.