The Soviet government did not have a true source of legitimacy.
Revolution was wanted by the people, as World War I was vastly unpopular and the weak .
Democratic government may have been even less popular. The skill and tact that the Communists utilized to come to power was admirable, and that is why they were able to grasp the reins of the country, and not let go. The power to brainwash most of the people in the country, most notably the military, was the key element to controlling the country. Other than the legitimacy drawn from within Khrushchev, Brezhnev, and Stalin's own minds, there was no outcry of Soviet support.
The Russian political culture is characterized by frustration and hostility. This is due to the horrors incurred over the 70+ years of non-participative government. By the time the citizens were allowed to voice their opinions, they are so fed up that all they can do is express their pent up anger.
Karl Marx's vision of a revolution was predicated on a small elite exploiting a large, educated, and organized middle class that would eventually rise up and overthrow their oppressors. From here, it would spread to smaller, weaker nations. Instead, it occurred in a Russian country that had none of the aforementioned qualities.
By the time Russian citizens were able to voice their opinions in the early 1990's, they had nothing but memories of oppression and terror in the Soviet Union. Thus, Russian political values are lacking, in that most citizens are very suspicious, hostile, and angry.
The USSR was not evenly split upon ethnic lines. Different races were just slapped together into different countries. Nearly all of the countries that split from the USSR (Armenia excluded) have a sizable Russian minority. A good example of an effect of this randomized drawing of political boundaries is the on and off was between Armenia and Azerbaijan over the province of Nagomo-Karabakh.