Why are there so many bands (particularly dadrock) that sucked utter dick from the turn of the 90s - early 00s before bouncing back in a big way? The slump usually happens immediately following their zenith, but that time period had far more than any other.
a-ha - Made those songs everyone knows, even got a fucking Bond theme that sold like wildfire (as it naturally does), made it into the 90s with an even stronger follow-up, then flopped for most of the decade until that concert in 1998 that sparked a comeback album 2 years later
Carlos Santana - Wallowed in irrelevancy in the years following Oye Como Va on record labels ran out of sweatshop basements until that 1999 album with around 6 million features on it
Depeche Mode - Had some strong showings early on, made Violator which almost no-one thought would do well, plateaued with its sequel, regressed from there
Genesis/Phil Collins - One of the most consistent artists there ever was, made 12 years' worth of runaway successes, then left Genesis for some Scottish nobody whose greatest claim to fame was performing an advertising agent's boyhood dream song to sell shitty jewish jeans before making that awful Papa Bear album or w/e it was called
Killing Joke - Literally one good album over the course of nearly 20 years from Night Time until KJ '03
Metallica - Couldn't get going again until Death Magnetic, Load and Reload were so-so coming off of the Black Album, St. Anger speaks for itself.
U2 - Reinvented themselves with Achtung Baby, then it took another decade before they even had a single song that approached that level again
What happened? It didn't matter if they started in the 60s or the 80s, the 90s made them practically extinct and the 00s dug them back up.