Russia was under the control of Tsar. He commanded the army, owned much of the land, and even controlled the church.
During the period before the Russian Revolution, life was difficult for the working class people and the peasants. They worked for little money, most of the time they didn't have food, and were exposed to dangerous working conditions. The aristocrat class treated the peasants like slaves, giving them few rights under the law and treating them almost like animals.
Because he had total power, they thought that he was dangerous.