Didn’t Stalin kill millions of socialists in order to wrestle control into his hands? Weren’t Bolsheviks explicitly anti-socialism?
Bolsheviks were "socialist" because at the time socialism and communism were largely interchangeable terms; you might be thinking of the various factions with "social" in their names that vied with Bolsheviks around the revolution (Social Democrats, Social Revolutionaries). Socialism certainly didn't have the "softer" connotation it has now.