Pre-Nirvana, you had Vanilla Ice, MC Hammer, C+C Music Factory and Michael Jackson at the top of the charts.
Post-Nirvana, you had a return to guitar driven rock music.
I think you make a good point. But remember, Nirvana wasn't the only band making headlines in the early 90s, there was a whole wave of bands defecting from the synthesizer. You might say that Nirvana was the most popular, though, depending on who you talk to.