>>17807525 (OP)They didn't, the communists had support among a sliver of the population (industrial workers in big cities) while the vast majority were peasantry who were either SRs (real socialists) or politically unengaged. The communists couped the democratically elected SR government because their power base was in the big industrial city of Petrograd and basically shot or completely sidelined everybody in every other town or village who disagreed with them.
https://youtu.be/8xaqVf1B3Fg