According to John Lewis Gaddis, in "The Long Peace" why didn't the cold war erupt into a full scale one between the USSR and the U.S.?

In my opinion, Gaddis presents two main arguments as to
why the Cold War did not ever become a hot war.  One is the polarity of the
international system during that time.  The other is the relative isolation of the two
countries.

Gaddis argues that the world was bipolar during
the Cold War.  He says that this helped bring stability because there were so many fewer
opportunities for conflict to arise (unlike in WWI, for example, where there were all
these powerful countries with changing and complicated
relations).

Second, Gaddis says that the US and USSR were
less likely to go to war because they had so little to do with one another.  There were
not constant interactions that could lead to conflict.