What are some causes of the 1984 Summer Olympics?

Of course, the ultimate cause of the 1984 Summer Olympics
in Los Angeles was the recreation of the Olympic Games in 1896.  But I do not imagine
that this is what you are asking about.

The main reason why
these games were important, historically, has to do with the Cold War.  I would point to
this as the "cause" of the games.  The main fact about the LA Olympics was that the
Eastern Bloc boycotted the games.  This happened because of Cold War tensions. 
Specifically, it happened because of the Soviet invasion of Afghanistan in 1979 and the
US boycott of the Moscow Olympics in 1980 in protest of that invasion.  Because of the
US boycott in 1980, the USSR and its allies boycotted the 1984
games.