who was outside of one of the power conferences, could get a prestigious national broadcast by agreeing to Thursday night. Then the lesser power conference schools jumped in line and Thursday nights became very crowded. But for a while schools like BYU and Boise were getting more national broadcasts a year than lots of power conference schools simply by agreeing to play on Thursday nights.
Also mixed up in there was the mtn debacle with the associated ESPN blackout of the MWC, which opened the door for Boise to step into that Thursday night slot for a bit.
The advent of games on ESPNU, ESPN News, and ESPN+/conference channels (as well as Fox and FS1) has lessened the need for scrambling for Thursday night exposure, and we've seen most power conference schools return to mostly playing on Saturday to better accommodate the stadium fans.