[WS:] It is a really interesting question. The "standard" left-wing interpretation holds that fascism was simply a capitalist reaction to the "communist threat." While there is some truth to it, I do not think it was a decisive factor and there is far more to it than the "reaction" story tells us. The growth of fascism in Italy and Germany was driven, in a significant part, by the domestic factors - especially the availability of paramilitary groups composed of the demobilized WW1 soldiers and officers. Their effective mobilization by the fascists rather than the communists (as it had been the case in Russia) was the key element of the fascist rise to power, especially in Italy. The other important factors include the Great Depression and the fact that the Nazi party offered an innovative economic plan (a variation on the Keynesian theme, if you will) to combat it, which greatly increased their popular appeal in Germany. In fact, the anti-Semitic and anti-Bolshevist shrill of the Nazi press subsided considerably after 1929 and was replaced by messages offering realistic solutions to the economic problems.
On the other hand, the success of the October Revolution was more of a liability than asset to communist parties in Western Europe. For one thing, it created an illusion that a revolution can be achieved in a similar way in Western Europe - which made Western communist blind to other options, so to speak. Of course, Gramsci (and Bordiga) realized that trying to emulate the October Revolution in the West was doomed - but he did that too late, when he was already in the fascist prison. But from that pov, a possible counterfactual without an October Revolution is that the Western labor would have developed a different than emulating Bolsheviks method of gaining political power - and probably a more successful one, judging from the cases of Sweden and Norway. In this case, the absence of October Revolution could have prevented the rise of National Socialism.
Wojtek