Other thing to consider is that UM has no control over the start time for its home conference games that were picked up by Roots because of the TV deal. UM can ask for certain time slots, but is at the mercy of how Roots wants to schedule its TV slots available to Big Sky teams.
Once Roots announced its TV schedule, that then allowed UM to negotiate with other TV partners to fill the void, as well as try to figure out if they could make a night game work with the visiting teams. South Dakota, Liberty and Southern Utah probably assumed an afternoon game and planned according to that, and then it was up to them to decide if they wanted to adjust their travel plans.
Liberty and South Dakota will fly commercially or charter, and if it is a commercial flight, they are locked in and hard to adjust their travel plans. Can't blame Southern Utah for saying no thanks to getting on a bus after a night game and getting back sometime Sunday afternoon in Cedar City, especially in the middle of conference games. (although perhaps they would fly...although probably would have to bus to SLC or Las Vegas and then fly out due to the size of the travel party. Unless that airport can handle a larger plane for that large of a travel party.)
I am sure UM would have liked to have a night game, but it is not as simple as saying "let's have a night game!"