From what I know about Cobain, I can tell you he probably didn't want to be labeled the way he has been labeled by the media for the past 10 years. I think he felt so much pressure from all angles. I'm not sure Courtney Spungen helped matters either.
As with all things new and exciting, they tend to fade once the clones creep in and try to cash in. But I think that Cobain really loved and cherished music in a way that only a real artist can. He was the real deal, trying to make music for the right reasons. But I think he knew and was able to foresee what his music had done to the industry, and yes, I really do think Nirvana's impact was that big. If you had to narrow it down to one factor or band, it was them. And he probably hated himself for it. I know I shouldn't psychoanalyze him, but in a way I think it just makes sense that Cobain realized that he had helped create (or at least make popular) "alternative rock" as a major genre. Lollapalooza demonstrated that there was indeed an audience there.
But to paraphrase Johnny Rotten, if you want to stop being a rock star then just STOP. It's that simple. And I believe that it's true. In my opinion, Nirvana happened because they were at the right place at the right time. So many brilliant pieces of music never get heard on a large scale because people aren't ready to listen. Cobain's legacy will always live on because of how he sealed his fate. Like all great art and artists, death at one's peak guarantees immortality. And as a result, those artists become legends. So there ya go. His music still holds its own, of course.
And for the record, yes, the Pumpkins in concert made some people lose their shit as well. "I Am One" live and "Silverfuck" always went over big. I do miss those shows back in 1993 and 1994. They were really soemthing.