R145 is on to something, there's an inherent classism and socio-economic agent embedded in the change. The 90s was the decade that record label execs, radio stations and record stores started keeping closer tabs on their sales and spins, meaning that the music biz was no longer so much about innovation and rejuvenation and more about moving product. By 1992 rap, r&b and country were found to outsell rock of any genre, and bubblegum pop was reinvigorating. From looking at the account books it finally dawned on the industry that the teens and 30-somethings were the market to target as they had most cash to spare, and so the youthful market of 20-somethings were cast aside. It was suits and store managers who became the tastemakers, over the geeky music nerds and critics who guarded the gates previously.

There's a more microscopic level to the end of hair-metal, too. By the early 90s, all the tortured American scenester rich teens who loved Crue as little kids decided hairmetal wasn't trendy anymore, and since tortured scenester rich kids were the ones still living in households with MTV on tap...they got to administer the killing blows. The cull wasn't even unwarranted, necessarily, as the time had come for a change and a new generation wanted a new sound as dictates the Circle of Life. The problem though was that, unlike in generations before, it was only the wealthy teens with money calling the shots on this change. The poor kids in the sticks or the trailer parks or without cable had to watch their rock gods and their message of optimism & rebellion thrown out into the trash for the crime of passé . This caused cultural schism and hurt, and a few years down the line this frustration found vent it what came to be known as Nu Metal (a hybrid genre of rap, metal & emo which was slammed from the outset for....yep, you guessed it, being trashy).

There's also the problem that after the 80s younger people stopped going to trendy clubs, as the economy took a huge downturn and it wasn't viable to go out every weekend and coke it up in the flashiest joints on the Strip. Grunge music, grunge fashion and grunge lifestyles were much cheaper and more low-maintenance than glam; all you had to do to be grunge was rip your jeans, steal some Docs and find an acoustic guitar in a pawnshop. It was a straight-edge trend so there wasn't even the pressure to seek out expensive habits like coke or speed or Cristal, better for high-schoolers.