I echo someone else in that the old Soviet Union helped to make track and field popular. Beating the Commies hooked people and I suspect they then developed interest in specific athletes (Americans were competitive from the 100m to the marathon remember) which led to interest in other events.
The Olympics were definitely more intense in the 70s and 80s because nations like the US and USSR were such rivals. It may have increased viewership of the Olympics and thereby exposure to T&F and marathoning, but I'm not sure that was the motivation for people to run marathons (ie, to beat the commies). I don't think there was a huge surge in ice hockey interest after the Miracle on Ice (1980), but maybe I'm wrong.