If $1000 total is bet on the BYU vs. UNLV game, they want $500 to be on BYU and they want $500 to be on UNLV. They move the line to bring more money in on a particular side.

Here’s an example: say Georgia is playing Utah State. Say Georgia is favored by 3 points. Everyone would bet on Georgia to cover that bet (I.e., win by 3 or more), while nobody would bet on Utah State. So they move the line. Maybe you’re confident that Georgia would beat Utah State, but are you confident they would win by 35? What about 50? They try and find that sweet spot so you have half the people betting saying “yes, Georgia will win by more than 40,” and the other half saying, “I don’t know, but bet Utah State can stay within 40 points.”

I think you’re using BYU and UNLV as an example of a team whose fans don’t gamble (BYU) and one that does (UNLV fans in Vegas). I doubt the oddsmakers considers that at all. People don’t just bet on games their teams play in. They get because they like the value of a team in a given game. BYU prohibiting gambling doesn’t change anything at all.