If I had to point to one single thing that killed rock, it would be Smells Like Teen Spirit.
I'd say that US Congress relaxing rules on media ownership had more to do with it
" In 1992, the
U.S. Congress relaxed radio ownership rules slightly, allowing the company to acquire more than 2 stations per market. By 1995, Clear Channel owned 43 radio stations and 16 television stations. When the
Telecommunications Act of 1996 became law, the act deregulated media ownership, allowing a company to own more stations than previously allowed. Clear Channel went on a subsequent buying spree, purchasing more than 70 other media companies and individual stations.'
'With 855 stations, iHeartMedia(clear channel) is the largest radio station group owner in the United States, both by number of stations and by revenue. The 855 stations reach more than 110 million listeners every week, and 245 million every month. '
https://en.wikipedia.org/wiki/IHeartMedia