Turner set up WTBS and then CNN in 1980. As I was with the cable division of Time Inc, at the time that was a major distributor of WTBS (later TBS) I watched it very closely.
Turner started a lot with regular programming of music videos on WTBS that led to MTV. The distinction is that CNN was all news, all the time based on traditional journalism. It was not designed to be entertainment.
Murdoch turned cable news into a means of locking in audiences based on sensationalism with the less educated and increasingly threatened, white demographic. Walter Cronkite journalism was something to be sneered at. Murdoch's audience were easy marks already an audience for tabloid news, conspiracies, and the sale of gold certificates, and quack remedies.
Turner's background was radio and TV from the days of federally (FCC) mandated balanced reporting. Murdock was from the British tabloid press with gossip, outrage, sex, and Martian invaders. Murdoch made a lot more money than Turner and so, became synonymous with cable news.