Discussions started Wednesday morning and a game was agreed to by Wednesday afternoon. It was tentative at that point (depending in the Thursday morning COVID tests for Liberty), but secure enough to be announced to the coaches/players on Wednesday afternoon.

So BYU coaches/players were prepping for Coastal Carolina from Wednesday morning/afternoon (3 days notice), with 100% of their focus on that game (since it would either be Coastal Carolina or nobody)

Meanwhile, Coastal Carolina was in a more uncertain position, since they didn't know who the opponent would be. There was a chance it would be BYU and a chance that it would be Liberty. As a result, Coastal Carolina had to split their game prep on Wednesday, before getting word on Thursday morning that it would in fact be BYU. So that gave them 2 days of prep for BYU and 1 day of half-prep for BYU.

Of course, Coastal didn't have to travel, but that's also kind of the inherent advantage in a home game. The one thing worth noting is that CCU's offense was more unusual and probably harder to prep for than BYU, which ran a very good, but fairly straight-forward offensive scheme.