It is a phenomenon I only heard about, in the last 4-5 years or so.
The jist of it is that pop music and rock music exist in a cyclical environment that turns over every 12-13 years.
The first half of the cycle sees the rise of some dominant rock force, some new spectacular sound that takes the current market by storm. After a 5-6 years those sounds are over saturated and begin to fade away, the market is overtaken by the sounds of pop. Boy bands and pop divas spring to the forefront and we are blasted with dance hits, and catchy beats.
During the reign of the pop era we see music find its way into every aspect of our lives. The pop music is so widespread, that it opens the doors for many new areas of growth, programs like TD music deals and tv shows like Yo Gabba Gabba! are just a few new flavors in a world swinging together in pop harmony. Everyone is happy.
Then after the public becomes tired of which ever pop sound is permeating the airwaves, from the ashes a new rock n’ roll phoenix rises and the whole cycle starts a new. The music scene finds itself permeated with young artists, tired of what they hear on the radio, and pushing the boundaries of what they know, so they can force change. The young angst is overflowing and they just want to change it all.
Sometimes it starts as a single community. An area like the United Kingdom or even somewhere as small as Seattle, Washington can quickly become the hub for a new power. Other communities quickly glom on to the new sound and it grows and changes and it is all stuffed under a single moniker like Grunge or Orchestral Rock.
What was once the new thing, is now the only thing.
People get tired of it, and the whole thing slowly moves from cutting edge red hot passion and rolls into a fog of beige sameness.
The industry tires of the same sound. Those tired of it, and with ability to create, start forging into new areas.