The role of institutions in the development of fascism was far more important than those of popular sentiments, popular movements, or even class interests. The institutions of particular interests are the Prussian military that was never defeated in WW 1 and thus remained almost intact, but which was dismantled under the provisions of the Treaty of Versailles. They provided the organizational structure for the fascist movement. Same in Italy where demobilized military were the "muscle" of the fascist movement. The second institutional force was the Hohenzollern monarchy with its institutional apparatus - again not defeated in war but dismantled under popular pressure from the working class parties. Rather than disappearing, these institutions became the "civil society sphere" a nexus of private organizations working to undermine the republic and restore monarchy.
Of these two, I think that the politicized military was far more important than the monarchist organizations. This can be demonstrated by observing the crucial role the military played in other fascist or semi fascist coups: Poland in 1926, Portugal 1926, Brazil 1930 and 1964, Spain 1936, or Chile 1973. I would go as far as saying that no politicized military = no fascism. Since politicized military is not a factor in the US or EU - the prospects of a fascist coup there are rather low, regardless of how much the grunts are disgruntled.
I also think that Marxists (with few exceptions, notably Gramsci) tend to underestimate the role of institutions and overestimate that of socio-economic classes. This is their major weakness as far as explanatory power of their theorizing is concerned -- Wojtek
"An anarchist is a neoliberal without money."