There were many factors which led to the collapse of communism in the USSR and all over the world( most of the countries). One of them happened during the late 1980s. During the late 1980s, particularly 1989 many of the European countries along the Eastern Bloc started to deny communism. Poland fell first and then down to Czechoslovakia, then Romania and so forth.
Communism was the government controlling the Society, meaning sealing from the people that should be actually getting paid more. Everyone had to be the same. Many people In Russia started to watch American Movies which showed the Russians how The Capitalists lived. The Russians wanted the same so they adapted their culture and as Mikheil came to power, he made the communist fade. As the Soviets turned into Capitalsts during 1990 and 1991, it spread the the Eastern Bloc for it to turn Capitalist too since there as no point of communism anymore.
The Berlin Wall was finally torn down as an official ending to the Cold War because it showed that the Soviet Union no longer supports communism.