Cobain's disenchantment with Nirvana's music and desire to be recognized not as the "Spokesperson for Generation X" but as a talented songwriter, his heroin addiction and crappy marriage to Courtney Love coupled with the item below broke up Nirvana (and 1 depressed but talented mans brain)

*yes I do love Kurt's ability as a songwriter so don't say that I am making fun of his death or anything, but honestly I'm tired of all the blame being shot around (no pun intended) the point is he killed himself or if you believe he didn't whatever he's dead ultimately Kurt broke up Nirvana if he intended to or not is a matter of opinion.*