The amount of soviet involvement required in Germany during the 30s to have the communists come out on top (especially since the SDP was anti communist and non cooperative to its core) would be paramount to starting a full scale civil war there and then being forced to directly being involved military wise for the german communists in a open proxy war against the liberal/right wing side that would be backed by the entirety of global capital while you are...the USSR of the 30s. At a point where the USSR couldnt project that kind of power let alone defend from it . They industrialization, militarization , modernization etc wherent even halfway done. Chosing to openly wage a proxy war in germany and spain during the state of material and military development they were in the 30s would be paramount to suicide with an extremely high chance of those countries NOT turning red, being invaded by fascism while in a much worse position or just not achieving the objectives in spain and germany and collapsing internaly much earlier

After the war again the USSR had to rebuild the entire eastern front from rubble without imperialist or colonial extraction to back that transformation up . What particular revolution post WW2 you think about where the USSR should have been much more involved ? Vietnam ? How much more ? They still won there and had a pro soviet state. Cuba? They did. Join in on the Greek civil war in the 40s? Maybe. I am greek so this is really interesting what if tho i cant help but think this would end up in a Korean war situation and due to it being a war on european soil again years after WWII it could have expanded into even worse outcomes