Who supported the Bolsheviks?
A very large chunk of Russian society supported the Bolsheviks. Not all of them were committed communists, but they were all very unhappy with the monarchy and with the provisional government that succeeded it. This led to a great deal of support for the Bolsheviks in the October Revolution.
The army and navy, or at least their rank and file, were largely behind the Bolsheviks. The soldiers and sailors were very unhappy with the way in which World War I had been waged. They staged mutinies against the government because it wanted them to continue to fight.
The peasants were behind the Bolsheviks. They had been mistreated for centuries in Russia. They felt the Bolsheviks would give them land and a system in which they did not have overlords to exploit them.
The workers were also generally behind the Bolsheviks. They were unhappy with the inflation and shortages that had been caused by the war. They were unhappy with wages and working conditions. They felt that a communist system would treat them more fairly.
Thus, while we cannot say that everyone in Russia supported the Bolsheviks, we can clearly see that many large segments of the population did support them to a large degree.