The old "Godless Commies" business, I think.
It seems more that we just managed to outspend them (or more accurately, force them to try to outspend us to the point where their economic and socio-political system could no longer afford to be in a Cold War with the USA). Gorbichev tried to make the system hold on even at the cost of bowing out of the Cold War, but it the strain had been too much by then, and some of the satelite states and client states wanted out.
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