The main reasons are:
1. The Red Army which was composed of the people (meaning the workers and peasants) fought in the interest of the people whereas the whites faught against the people.
2. The Soviet system does not divide the people - it unites them!
3. The Soviet government consistently pursued a policy of equal rights for all peoples thereby strenghthening the position of a proletarian state.
5. The bourgeoisie was powerless against the people - ruined by their own subversion and corruption.
6. Plus hundreds of other answers.