I tend to think it is more of a combination of things.
For the oldest of Germans, it is the slaughter of WW1 followed by the destruction of nearly an entire generation in WW2.
For the Middle-aged ones, it’s the divided country and the occupations, both Soviet and Western.
For the younger ones, they only know what they have seen in the movies.
I completely agree, no culture can endure those kinds of losses without a profound psychic hangover. Yet, those with personal knowledge of the first world war are now long dead. When I first came to Germany one saw in a neighboring town which was designated a Kur Ort (cure community) men of a certain age missing an arm or a leg on the streets because they were in town to be treated. They too, are no longer to be seen. Somehow, the legacy has survived these generations and, like a virus, lives somewhere deep in the body politic.
If one has exposure to the German school system as I have with four children going through Gymnasium, one can but conclude that the entire system is green and leftist. Somehow yet quite understandably, the German establishment has taken the wrong lessons from the experience of World War II. For example, it bans certain parties, it opposes certain groups like Scientologists claiming to be religious, it squelches free speech concerning the Holocaust, rather than guaranteeing liberty. This tendency is understandable to the American mind only when the horrors of those wars are understood.