The main reason we can point out is that Eastern European economies were under the influence of the Soviet Union (SU), and Western European economies under the American Marshall plan. The American plan aided billions of dollars to those countries in order to rebuild the social, political and economical scenario after war, while the SU worked under the rules of communism. The inefficiency of the centralized Soviet Union, and consequent iron wall that isolated the eastern European countries from trade, aid and economical development with other countries contributed decisively to the lower economic growth under those countries.
Within the decades the Soviet Union proved itself a failure of a system and finally collapsed in the 1990s. This generated a successive process of independence and a marked the change from communism from capitalism in the former eastern countries under the soviet influence.
