Rock bands are expensive to operate as businesses, and generally full of dickish personalities with enormous creative control and ego issues.
The 90s gave rise to flagrantly auto-tuned pop idol groups, so-called "reality television", and a host of other forms of extremely low-cost, high-margin entertainment. Which, by the way, was always "studio led", reducing control issues over even fairly big stars.
It was also a period that included the impressive rise in power and sophistication of the (largely dial-up) Internet, which in turn provided many additional entertainment outlets, and the ability to "feel part of the group" in a much less geographically-specific way… You could be a proud proto-goth, without having to blend in with the skinheads or metal stoners at your high school. Did I mention video games? VIDEO GAMES. Frag. Men. Tation.
In short? The music business gave up on arena rock. It was too expensive, too much a pain in the ass, and required large affluent audiences to concentrate their entertainment dollars all in one place, precisely at a time when they were "spreading the love" across a greater number of different forms of play/indulgence. It also didn't help that due to the transition to CDs, burgeoning internet use, the mp3, and services like(the original, not the current whatever-the-heck-it-is), the recording industry was undergoing multiple, drawn-out changes to their long-standing business model – one of which, at least, was entirely involuntary (so-called music piracy).
At the end of the day, all these guys cared about was money. And there wasn't a lot of money in promoting single rock bands in the 90s (though, for a time, music festivals likeexperienced a huge resurgence – again, by providing an alternative to the existing model – greater attendance in exchange for lower dollar-per-band in the cash box).