I think that a lot of film people are opportunists to the bone. They have to finance their films one way or another. Leni just happened to choose a disastrous time and place to be opportunistic, and when she was quite young too. So she had decades to repent.
I'm not sure that being young gets her a pass. I mean, it's not like Hitler made any attempt to hide his ideology or what he ultimately intended. To complain that art was taken away from her as punishment for helping such a monster, without acknowledging how her aiding and abetting of Hitler ended the lives of so many other artists -- Bruno Schulz, Pavel Haas, Hans Krasa, to name but three -- well, perhaps its better that she had to live so long and, one hopes, be reminded rather regularly of her own not negligible role in creating that horror.
I'm not defending her. I'm making the more pessimistic statement that lots of people who didn't do that, might have.