Grunge music started as a result of Heavy Metal music basically being dated in the mid-80's. Hair Metal and all that crap was getting huge, so bands like Green River and Soundgarden started writing music that was similar to fashion to the Punk movement of the early 70's. Kurt, being apart of this movement, made music in a sense for himself and not so much to make money. It was for enjoyment. The album Bleach was made on something like a $500 budget. When Grunge blew up, he became exactly what he set out not to become, which was this huge pop icon. He had a lot of problems to begin with, this on top of the realization of being exactly who he never wanted to be resulted in him killing himself.
I know a lot of people say he didn't kill himself, but it's one of those things we'll never know for sure. I personally think he offed himself. It's what I choose to believe. Quite frankly I don't care, I never knew the guy, but he wrote some pretty killer music. Bleach is the only Nirvana album I really care much about though. I've always been more of Soundgarden and Alice In Chains fan
And let's not forget, Temple Of The Dog. Though, I don't care for Pearl Jam either, they did damn well with Chris Cornell on vocals.