How did two revolutions and a civil war bring about communist control of russia

The first revolution toppled tsar rule and put a provisional government had little support,

This situation make it possible for the Bolsheviks second revolution to bring down the government. When the civil war was over, the Bolsheviks now replaced the tsar and hold the majority of control in the government. They later on replaced the officials that ruled under the tsar with their own, and implemented communist principle to Russian economy.