That's a pretty fantastical view. The Bolsheviks came in second, behind the SRs, who were fond of terrorism and were entirely backwards in theory and in practice. The SRs had also had a major split shortly before the election without most of the voters knowing. It was the bolsheviks that succeeded in carrying out the revolution, weathering the Russian civil war, and then solidifying the socialist state.

They didn't just murder anyone that had more support than them, that's a fanfiction view of soviet history. They were, towards the revolution, consistently the most supported among the working classes. The Left-SRs, who weren't really a coherent political force as the SRs themselves had a major split, supported the revolution and many ended up joining the bolsheviks anyways as the SRs faded away. The Right-SRs, who came behind the bolsheviks, had some join the bolsheviks and some join the White Army.

All in all, the bolsheviks were supported by the majority, and the CA was being phased out in favor of the soviets anyways.