Because the Allies essentially divided their European conquests. The Russians got their zones, the Americans theirs. Either side threw the dissect term in jail, Americans got rid of the communists, the Russians imprisoned the non-party people and voila.

In short, there was 1) the massive Soviet army that one of those smaller nations could hope to compete with and 2)the installation of communist parties by the Soviets to run the satellite states.

Marshall Plan participation was open to all, but the economic entanglement would not fit with Soviet plans and command economy. Czechoslovakia and Poland agreed to attend the Paris meeting but the Czechoslovakian foreign minister, Jan Masaryk, was summoned to Moscow and berated by Stalin for thinking of joining the Marshall Plan. Polish Prime minister Józef Cyrankiewicz was rewarded by Stalin for the Polish rejection of the Plan.

^Forrest ^C. ^Pogue - ^George ^C. ^Marshall: ^Ordeal ^and ^Hope, ^1939–1943