This is something I would like to study one day. There seems to have been a turn in German public attitude at some point. As far as I can say from what I’ve read, it haven’t yet happened in early 50′s. Denazification programme and Nurnberg trials were felt to be a farce a it’s unclear whether they could have contributed to the change. Some public figures (e.g. Adenauer) may have lead by example, but frankly, I don’t know.
If people here, especially Germans, have any insights on the topic, it would be great if they could share.
I haven’t studied this in detail but as a German common knowledge would be that the main change in public attitude came around 1968.
The hippies were influential in challenging the political status quo in many countries and changing the German public attitude towards the Nazis being very bad happened at that time.
There are also lots of different things that happened in the cold war where Germans felt supported by other countries. The military occupation that existed in Germany also allowed the Allies to do various small things to affect German public attitudes.