This question has been on my mind for a long time. I still don't have a fully formed opinion but I was hoping to form one that doesn't follow the bourgeois (the Soviet Union was an evil empire that collapsed because the people rose up and destroyed communism) or anti-revisionist Stalinist (the Soviet Union was socialist under Stalin and wouldn't have collapse if it weren't for revisionists like Khrushchev and Gorbachev) explanations.
My understanding is that the Soviet Union was a deformed workers' state, a dictatorship of the bureaucracy. In order to overthrow this bureaucracy and establish a workers' state under the control of the proletariat, a political revolution composed of and led by proletarians was needed.
It is also my understanding the the ruling bureaucracy of the Soviet deformed workers' state was not a class but a caste. It had political power but did not own the means of production. Because a class is inherently more powerful than a caste, the bureaucracy would like to restore capitalism and use its political power to gain ownership of the means of production and become the new bourgeoisie.
When the workers decide they have had enough of Stalinism, they begin to form a political revolution. The bureaucracy than co-opts that political revolution and leads the restoration of capitalism.
Is this correct?