Michael Burleigh says in Third Reich that the leadership of the Weimar Republic messed up royally when it refused to cultivate the feelings of nationalist attachment to the republic. They didn’t create a big, touching ceremony for the signing of the constitution. They avoided all pomp and circumstance. Refused to create commemorative medals for the survivors of the Great War.
This was a gigantic mistake because the Great War had only been possible because nationalist sentiment had been manufactured and people felt it strongly. Weimar’s incapacity to channel these feelings somewhere productive created an opportunity for horrible people to channel them into a horrible direction.
Obviously, this was far from being the only factor in the rise of Nazism but we all know about the other factors while this one is something I never considered before.