Yacht Rock a Dockumentary

Probably the biggest song right before MTV took off was Escape /Pina Colada - a song targeted for people in their 30s (ish) as almost all yacht rock was
The real sea change for Mtv is that the age demo shifted by a decade or two
It went from gearing to adults who were going to buy concert tickets to kids at home eating pizza rolls

And I think your inclusion of Bowie gets it backwards- Bowie, other glam rockers and funk bands like Parliment and EW&F presaged the visual elements of music
MTV did what Bowie, et al were already doing, not the other way around
Bowie was experimenting with making music videos in the late 70's with "Heroes" and some of his best, state-of-the-art recordings were done with Brian Eno in the late 70's/early 80's so I do see where you're coming from. David Bowie also helped rescue and resurrect proto-punk Detriot rocker Iggy Pop after The Stooges fell apart for the final time in 1974 and helped him kick heroin for a while so he started work on The Idiot. Bowie even toured with Pop in 1977 as his piano player. They both made a very famous appearance on the Dianna Rigg show during that U.S. tour in 1977.