The collapse of the Soviet Union at the end of the 1980's was a great blow to the hopes of revolutionaries. Why did it collapse? The primary causes were political and economic and they were the result of the culture of war.
The immediate cause of the Soviet collapse was economic, as the Soviet Union lost the arms race and international competition with the West. The United States was able to profit from its imperialist exploitation of other countries, while socialism could only lose economically in that competition. By the end, the ruble collapsed as Soviet consumers turned to imports to satisfy their needs. They could not buy a good pair of leather boots or a good television set or a computer made in the Soviet Union, because all the boots and the electronics were swallowed up by military procurement. And, needless to say, there were no quality goods to export in order to balance imports.
Economic factors were linked to political and psychological factors. As the Soviet economist Latsis said at the time, "the gloomy background of the worsening market situation ... has a depressing effect on people." Their gloom deepened as a result of policy failures such as the explosion of the Chernobyl atomic power plant and the war in Afghanistan (see US military analysis of Afghan war).