There hasn't been great scholarship on the buildup of Fascism - or at least there are some big missing pieces.
So many records were destroyed, and until very recently, propaganda was still sacrosanct.
In Communist countries, Fascism had to be Capitalist reaction to working class solidarity. In Western Countries, there was more freedom, but there was a strong stigma against any analysis that violated Atlanticist principals. Hannah Arendt's "Eichmann in Jerusalem" raised too much controversy for claiming Eichmann was just a joiner, not hateful.
Until recently it wasn't just propaganda, but a basic human decency not to ask certain questions too loudly while the survivors of the Holocaust were still alive, and their persecutors lived unpunished.
For example, there's little willingness (in the West) to discuss the role Russian emigres played in supporting Fascism? They were obviously being opportunistic, as were Ukrainians and Finns.
I learned very recently that in late November 1918, weeks after World War I ended, the British told the Germans they could expand Eastward, rearming if necessary, to prevent the Bolsheviks from advancing.
The Germans had already disarmed, and no longer had functional militaries. But they were able to raise self-sustained militias that moved into parts of Poland and Lithuania.
Later on, Nazi propaganda played up this fact, while Allied propgandists chose to ignore it. It likely had a role in convincing Germans they had a "natural" claim to East Europe.
Looking at the news, the German army recently held marches in these places, as a sign of support for NATO against the Russians.
Compare: "This video on pulling weeds is useless, because after the tree has grown it has a mighty root-system."