I would say that the problem is a lot older, more fundamental and anchored on two issues:

• Somebody else got rid of the Nazis, not the German people, and all the subsequent learning from Nazism was the result of outside pressures and based on an outside way of thinking, rather than being the result of self-discovery and self-improvement.
• The "lessons" learned were structured in the way of thinking of the 1950s which was still very much normalized Racism, so instead of the lesson being the modern Humanist "This should never be allowed to happen to anybody", it was instead the highly Race-specific formulation of "We (Germans) should never do this to Jews again".

The result is that the mental architecture of seeing people as members or races and hence assumed to have a certain nature based purelly on their race (good, bad, trustworthy, untrustworthy, victims, aggressors, oppressors, oppressed and so on), that formed the foundation upon which Nazism was built, was never abandoned and instead only the list of "good" and "bad" races changed, which in the domain of Prejudice and Racism was but a tiny step away from Nazism.

If in the mind of most of a society, people's worth and deserving of special treatment is determined by their race to such a point that, as we saw with the "unwavering support of the Jewish Nation" during them committing a Genocide, even extreme negative behaviour of people is acceptable if they are members of a race deemed "good", then all the mental pathways to think and act exactly like that towards "our race" - the mindset of AfD - are in place and well travelled.

Nativist Racism in Germany is the harvest of a field well plowed and fertilized with Racist and Prejudiced practices (described as "positive" to make them sound like a good thing) for the last 6 or 7 decades. Worse, that well kept field was the very same were Nazism blossomed over a century ago.