For the NFL, halftime is the Superbowl’s great money spinner, and it is made all the better by expanding the audience demographic to include more women, teens, and non-sports fans. The halftime entertainment is selected to do just that.
Actually the NFL really doesn’t care about the halftime show. They made their money selling the broadcast rights, the network likes a good halftime show, helps sell more ads. The league neither makes nor spends money on the halftime.