Well I think the key sentence here is: "...all he wanted was acting, because he loved it." He was working on a film, doing something he loved, pushing himself hard.
He was always very energetic — almost hyperkinetic. People with that makeup (in whatever profession) frequently have issues with not being able to rest. He worked through the middle of winter with many other people around and probably contracted walking pneumonia — a hazard for anybody, star or not.
We feel so intensely for him that we may assume (or wish) that those feelings may affect his destiny some way or another. But I just don't know that the level of adoration from Brokeback fans really comes into play here.