for the 8:15 PM ESPN time slot. There just isn't any other teams out west playing home games that week. Only other team in the Mountain or Pacific time zone in a P4 conference that is even playing at home is Colorado, and I think BYU is more likely to fill that spot than Colorado.
I guess theoretically they could grab a MWC team to fill that game, but Boise St. is already playing on FS1 in the late-ish spot (7:45) and the ESPN spot typically goes to a P5 team (historically either PAC-12 or BYU) and I think that's the direction ESPN will lean here.