Utah is letting KW go despite the fact that KW has had a far more successful career than BM.
Just this year, Utah went 5-4 in the tough PAC-12, good enough for a Las Vegas Bowl berth where they trashed Colorado State. BYU went 8-5 against a much weaker schedule, while Utah was 4-0 OOC. BYU lost to Utah State, Nevada, UCF, Memphis and Boise State, and only beat 1 team, Houston 7-5, with a winning record. Utah lost to #2 Oregon, #10 Arizona, #15 Arizona State and Washington State, while beating #24 USC and UCLA. None of BYU opponents ended up ranked. BYU was ranked early on but dropped off after the Utah State debacle. Utah finished the season #22 and will probably rise into the Top 20 after the Las Vegas Bowl win. Of course, we know their head to head record, with Utah winning the past decade handily including the last 4 in a row.
BYU seems content to see BM take them to their foreordained minor bowl with a nominal winning record against patsies, while Utah wants more than KW is offering from the PAC-12. I can't say if Utah is right to can KW after a decade, but he certainly has done more for Utah than BM has done for BYU, especially over the past 7 years.