I don’t know if I can blame MTV for the demise of rock bands and rock music in general, but it has been apparent to me for several years that rock music is dying and rock bands as I understood them are becoming an endangered species. What we have now are rap and divas (e.g., Beyoncé, Ciara) and singer/celebrities (e.g., Justin Bieber), not rock bands or rock music.
Check out the Frank Zappa video linked in dfwgator’s comment 94 on this thread. He sums it up a lot better than I can.
MTV was a transition from music, which is primarily audio, to video, which is all visual. The audio/music withered. That’s why the genre is dying.
There were good bands in the 1980s when MTV came around...but not much past that. They are not supported by the current format.