I think it has always been clear among most objective historians that there is little difference between fascism and communism. My take has always been that “fascism” was the word that leftists use to smear rightism as potentially dictatorial. Rightism *is* potentially dictatorial, but the end result is no different than dictatorial leftism.
That’s one reason among many that I like Mises’ terming fascism “socialism of the German pattern,” and communism “socialism of the Russian pattern.” It’s linguistically a little clunky, but still makes for a great terming of the concepts.
Jacques Delacroix has gone to great lengths to explain this concept as well here at NotesOnLiberty. For more on the similarities (and confusion) between fascism and communism, see Fascism Explained and How ’bout Communism?