When World War II ended, Europe was totally destroyed and at the same time, the Soviet Union terminated her relationship with the western alliances. In terms, the countries in Western Europe wanted at all cost to stop the proliferation of communism. It was important to Western Europe to begin the reconstruction of its economy as an efficient tool against communism. They pay special attention to Italy and France, which after the end of WWII had a big number of communist organizations.
Furthermore, The United States was very aware of this situation, and they decided to put billions of dollars into the economics of Western Europe to Guarantee that there will be economic prosperity in the area, hoping that a capitalist system could deter any attempts of communism to expand. The name of this strategy was called, The Marshal Plan.
Finally, due to this actions, an economic integration was achieved, also helped by the Treaty of Rome in 1956. At the end, Capitalism was firmly established and it contradicted with was happening in Eastern Europe.