Agree 100%, and that it was an outgrowth of the 70's. MTV would not have been big 10 years earlier with a glam approach. I don't think they led the "way". They were on the cutting edge of that "way" as it evolved.
People knock disco, but there was stylish club scene preceeding the 80's, with clubs barring patrons wearing jeans and sneakers. Look at the first disco scene with Pam, Bobby, & Lucy...no grunge clothing there (tho' Texas has always been forgiving of the 'boys wearing jeans and the hat).
The thing that amazes me is, as you put it, "an outgrowth of the 70s", which the 80s was, just as any decade is an outgrowth of the previous decade, is how much the look and attitude of the 80s was so markedly different from the 70s. It was such a big change, evidenced by the glam style that you noticed whether watching Dallas or Dynasty, MTV, or listening to 80s music. I think MTV pushed the "glam" aspect far past what it would have been had there not been an MTV. Music was concerned with visual image to an extent far beyond what it had been, and you can probably think of 80s bands that seemed more concerned with their image than their actual music.
If MTV had been able to begin in the early 70s I agree that the videos wouldn't have taken as extreme of a glam approach. I think it would still have made musicians more image oriented than they had been, but not to the extent they took it in the 80s. There must have been something else driving it in that glamour oriented direction.
@Karin Schill and you both made a good point about the economy of the 80s, how the middle class thrived under the Reagan administration. In the 70s people were getting over the Vietnam war, Watergate, and in a stagnant economy. Then in the 80s, Vietnam and Watergate were further behind, we had a president who was genuinely liked, and the economy was booming. It was like a malaise lifted and people began to be much more optimistic. The future looked bright. That reflected in the style of the decade and it was very distinct.
I don't think we've had a decade as easily visually recognizable as the 80s was - someone could show you TV show from the 80s and even if it was something you'd never seen before, you could tell it was from the 80s. You can hear music from the 80s, even a song you haven't heard before but the music and especially the production will have a distinct 80s sound. The 2010s were not nearly as distinct from the 2000s as the 80s were from the 70s.
Do you think the 2020s will have their own distinct style like the 70s and 80s both did, or that we'll see more of the same as we did in the last 20 years, where the decades were far less distinct from each other?
... and the best of the lot... 
