The great book Socialism Betrayed, written by Roger Keeran and Thomas Kenny, explains that, along with economic factors such as the "second economy" and international pressure from imperialism , revisionist and opportunist "forces oppos(ed) socialism from within" the Communist Party of the Soviet Union. There were 'two trends in Soviet politics'--a "leftwing Communist tradition represented in the main by Vladimir Lenin, Joseph Stalin and Yuri Andropov" and a "rightwing Communist tradition represented in the main by Nikolai Bukharin and Nikita Kruschev." And "the Soviet collapse occurred in the main because of the policies that Michail Gorbachev pursued after 1986." Keeran and Kenny declare that: "after 1985, Gorbachev's policies moved to the right, in the sense that they involved what might be called a social democratic vision of socialism that weakened the Communist Party, compromised with capitalism and incorporated into Soviet socialism certain aspects of capitalist private property, markets and political forms." (Roger Keeran and Thomas Kenny, Socialism Betrayed: Behind the Collapse of the Soviet Union, 2004, International Publishers)
(Lenin put it squarely: "We raised the banner of peace and socialism for the whole world to see!")
Keeran and Kenny inquire: "...why could Soviet socialism not survive a Gorbachev?
"The answer is: the subjective factor is vastly more important in socialism than in capitalism. This is both a strength and a vulnerability. A qualitative difference between socialism and capitalism is captured in the saying 'capitalism grows; socialism is built.' At the risk of a tedious simile, the two systems are like a river raft and an airplane. With capitalism--the river raft--the pole man who steers the raft has to avoid shoals, rapids and waterfalls. Mostly the flow of the current down river controls the pace and direction of the raft. It is a simple and mostly automatic system. Only loose supervision is required. Big blunders are usually not fatal.
"An airplane--socialism--is a far superior mode of transportation. It's range, its freedom of direction and manuever, and its speed far exceed that of the river raft. But the airplane requires conscious application of the laws of physics and aerodynamics, forethought, planning, science, training, ground crews, radar and so on. It is a complex system requiring a massive social division of labor. Managing the system--its piloting, the subjective aspect of its steering--is far more crucial to the safe operation of this mode of transportation than is the case with the river raft. Big blunders in piloting a plane, though rare, are often fatal. There is a smaller margin for error. The fact that airplanes sometimes crash does not prove the superiority of the river raft. It is only an argument for better-engineered, better-piloted, safer airplanes.
"The laws of socialist construction differ from the laws of capitalist development. Capitalism's laws operate blindly, without consciousness, like the law of gravity that sends the river raft down stream, no matter what the pole man is doing. But socialism's laws, while objective, require an airplane whose designers consciously master and use the laws governing such forces as gravity, thrust, lift and drag, and a pilot skillful in the technique and grounded in the underlying science.
"Therefore a Gorbachev leadership could do far more damage to socialism than an even more blundering Hoover did to U.S. capitalism." (Roger Keeran and Thomas Kenny, Socialism Betrayed: Behind the Collapse of the Soviet Union, 2004, International Publishers)