had to move a Sunday game for BYU in 50 years? Never.
With 8 conference championships/tournaments on Sunday in the Big 12, they'd have to move every one each year for BYU. There's some lost TV revenue in there and you can bet they and their TV partners don't like that.
From people close to a couple of Big 12 programs, this was never going to fly and BYU as full member of the Big 12 was a non-starter from the get go if we wouldn't budge on Sunday play.