What event could have helped spread communism throughout europe ?(including the west)

The two most obvious answers are either the communists revolts succeeding in Germany in 1919 or the Soviets winning the Soviet-Polish war. Another is maybe if Malenkov managed to stop Khrushchev from coming to power which would both stop the USSR from becoming revisionists and leave no basis for the Sino-Soviet split.

A successful German revolution circa 1917.

Success of German and Hungarian revolutions or avoiding the Marshall Plan. Europe was in ruins after WWII and the US said they would only give assistance to countries that voted for right-wing parties. The CIA also infiltrated the elections of France and Italy to stop communists from winning, since they were very popular after leading the resistance in the war. At the same time, the British and US helped monarchists defeat communists in the Greek Civil War.