I never understand, how the cable channels such as MTV, got away from the programming they were set up to show.
MTV was music television. VH1, Video Hits 1, was another music video channel. Ditto CMT, Country Music Television.
And there are many others which have gotten away from the reason for their creation. A&E, Arts and Entertainment channel, never has highbrown arts and entertainment programming. The History Channel seems to have reality shows nowadays. The Learning Channel, TLC, seems to have mostly reality and very little dedicated to education or learning.
The world of cable TV seems to be a jumbled mess, in terms of what programming is found on which channels.
In MTV's case, they basically started out airing entirely free content. The record companies gave them the videos to play for free in the hope they'd sell albums. It worked and everyone was happy.
Eventually, there were more videos than hours in the day to play them and money started changing hands which is called "Payola" or "Pay to Play" and illegal. MTV slowly started to move away from music videos and pioneered Reality Television, another media that costs almost nothing to produce.
A very good book explains it all.