It’s a little disingenuous to believe every failed revolution contributes to the one successful good outcome.

Contributes? No. But you don't know which attempt will succeed until the whole conflict is over. That's not an excuse to say "Well, this will be bloody, so maybe instead we just stay under feudal authority." You can't do that; you have to press forward.

The Spanish Civil War oversimplified basically boils down to this: one side, the nationalists, that supported the military regime and the Nazis and provided supplies and mainly logistics for them, and one side who decided it was better to throw their bodies into the machine until it stopped turning. The side with the Nazis won the war. Since the Nazis were at war on multiple fronts, there few allies were key in prolonging the conflict and defending Germany.

... I don't know that I follow this? Nazi Germany wasn't at war, for all intents and purposes, until '39, by which point the Spanish Civil War was wrapping up. The Republican side didn't try to 'throw bodies into the machine until it stopped turning', the war was highly contested and anyone's game for the first two years.