The sad thing about the entire movie is that Apollo could've easily lived
There is really no reason (other than I suppose a pride and ego issue) for Apollo to get back into the ring and face Ivan Drago. He by the looks of it, is financially stable, thus it isn't like he needs the money. And it isn't like Drago goaded him into fighting him like Clubber Lang did to Rocky in the previous movie.
Or even he himself did to Rocky in the second movie. But in that case, it made sense since Apollo wanted to shut his critics up about Rocky "going the distance" not being a fluke.
And as Adrian tried to tell him, he had been formally retired from competitive boxing for many years. Rocky himself added, that they didn't know anything about this Russian guy.
I know that within the context of the storyline, the Cold War was still raging and the Soviet Union was being painted as the arch-enemy of the United States. But on the outside looking in, why should I care if a Russian is good a boxing (other than the stuff about Drago being chemically enhanced)?
Boxing is an individual sport, where essentially, everybody is out for themselves. This isn't exactly the Olympics, where there's a built in reason to want to root for your country.