Nirvana were influenced by some large bands that are still around to this day, like The Melvins. Nirvana just happened to have tweaked their sound and been in the right place at the right time. I do enjoy Nirvana, but bands like The Melvins have a far large catalog, and there were quite a few other bands that influenced Nirvana that kept going. Nirvana did often shout out these other bands, but people were too hooked on MTV back then, and weren't as willing to look up the bands they would mention.