It was because of USSR that socialism rose in Eastern Europe. Looking for areas of influence they approached these countries that, astounded with the Soviet "wealth" accorded to use this socio-economic system. When socialism began falling, mainly in 1989, it represented not only the decay of the Soviet Union but of socialism as a whole.
P.s. Note that there is a huge difference between socialism and communism. The first one is the state through which a nation has to go through to become a truly communist country, where everything is shared. Also, communism is anarchic. Both are horrible systems but it's important not to misunderstand some basic concepts.
