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