"plant the Hammer and Sickle flag on the surface that will enslave the world in Communism"
Command of space ( not necessarily the moon, but earth orbit for certain ) would be a huge strategic and tactical advantage.
If the Soviet Union had managed LEO or the moon, do you think they would have not used it?
China, 1941, 1945
Support for NKorea, 1950
Support for NVietnam, 1961
One can argue Crimea, 2014, but that isnt "Soviet Union".