Karl Marx espoused his theory that industrialized societies would eventually undergo communist revolutions. Historically however, the only nations that have become communist were underdeveloped or undeveloped, as ideological modifications of Marxism were used to promote either that industrialization could take place under socialism/communism, or even that industrialization could be largely bypassed in favor of a peasant-based agrarian society.
The one major exception was Germany, Marx’s country of origin. Between the end of WW1 and the rise of the Nazi party Germany was the only fully industrialized country that could plausibly have had a successful communist revolution. A communist Germany beginning in 1930 would have been the closest approximation to Marx’s original vision possible. How do you suppose it might have shaken out?
My guess is that after an initial period of detente’ Germany and the USSR would have had a falling out; the leaders of an independently communist Germany would not have cared to be lectured or dictated to by the Kremlin. Maybe Trotsky would have taken refuge in Germany and there would have been a schism between pro-German and pro-Russian communists throughout the world. It might (or might not) have made a dent in the paranoia of anti-communists throughout the world to see the “world communist movement” so glaringly divided. I have no idea how the Spanish Civil War would have been changed; it depends strongly on whether the schism would have further weakened the Republican forces or whether the rival communist groups might have formed a grudging truce and alliance. Poland’s fate caught between the two rivals (who might have the dismemberment of Poland as the one thing they could agree on) and whether another European war might have eventually broken out, I don’t know.
It’s also interesting to speculate about Germany’s internal history after a communist victory. If there was little or nothing to be done to promote further German industrialization, then party doctrine would have had to focus on running the appropriated industries along communist lines. During the worldwide Depression simply feeding the workers on a soup-kitchen basis might have been initally popular and succesful. However I suspect that the inevitable idiocies of running a centrally planned economy would have taken their toll after awhile.