The issue ESPN has is the contracts with the various conferences, which guarantee that the conference will get certain timeslots (or some number of a timeslot, such as the prime time ABC game). The game is on ESPNU because of the contract with the Sun Belt only requires ESPNU and they are contractually obligated to provide other conferences the evening timeslots on ABC, ESPN, and ESPN2.

I believe what ESPN hoped was that at least one of the games slotted for one of the better channels would be cancelled, due to COVID — allowing them to move the BYU-CCU game to the better slot. Since those games are not being cancelled (and there seem to be fewer cancellations this week, overall), ESPN can't move the game.