[InclinedPlane]

MTV blew up because of a very specific set of circumstances.

First, radio stations were dying. They were being sucked up into nationwide conglomerates and changing from independent DJs with free reign to play whatever they thought was interesting to being forced into playing whatever generated the most revenue at the least cost with the least risk while cramming as many commercials into every hour as possible. In short, becoming soulless, disenfranchising people with interest in niche or innovative music, and most especially abdicating their former prominent role of being a place where people found new music.

Second, MTV happened to be launched at a time when there were very few music videos. Since they had no budget for any other programming they had to play a very eclectic mix of music, they couldn't afford to pick and choose much. They thus became one of the most avant garde radio stations in the entire US and became one of the only conduits between a lot of innovate new music (metal, punk, etc.) and a ravenous demographic (teens) who were otherwise cut off from that music due to the diminution of radio.

Once MTV had significant revenue they fell into the trap of thinking they needed "real" programming instead of just music videos, and that thinking persisted until almost all of their music content was driven away. MTV is now about as relevant as the average irrelevant pseudo-local radio station.