The general jist is that the communist method of identifying fascism is as a counter-movement to communism. Fascism arises wherever leftist revolutionary movements are reaching a point that will endanger the state, the capitalists fund fascism to acquire the tool of unlimited violence to use against the left to crush the threat, then they transition back to liberalism which is a more efficient extractor of value than fascism. This protects liberalism from being blamed for the violence and yet handily allows the bourgeoisie to use it. Fascism is the antibody of capitalism, the white blood cell that cleans capitalism of the communist infection to protect it. We understand fascism to function this way and to transition back into liberalism rather than becoming its own distinct thing because that’s precisely what happened everywhere that fascism won, fascism simply transitions back to liberalism later after achieving its task.

With this method of identifying fascism in mind the social democracy in europe that arose post-ww2 was implemented to deradicalise leftist movements by providing compromise with the workeers without ending capitalism. This functionally carries out the same thing fascism does but through a different method - cleansing the population of radicals by changing the material conditions that cause those radicals to occur.

In this way it is the “moderate” wing of fascism, performing the same goal fascism performs but through different means. Prior to the implementation of social democratic concessions communism was spreading across europe, social democracy stopped it.