MTV didn’t just appear out of nowhere. Not that it wasn’t a gamble. The very idea of a cable channel sustaining itself with a 24/7 rotation of music videos baffled all the major US labels, who saw such visual promotion of the latest singles as perfunctory at best. In a few short years, MTV went from broadcasting to a cluster of households around the New Jersey area in 1981 to completely reshaping the music industry and the decade’s pop cultural …