10% to blame: The muffed punt rule
Early in the 4th quarter, KU was punting the ball while up 17-13. Illinois muffed Kansas’ punt and the football bounced around for several seconds, even ending up in Illinois’ endzone, before the Fighting Illini fell on it. Since they never had true possession of the ball, the ruling was that it would be a touchback rather than a safety.
While entirely correct from a rulebook standpoint, it was a huge break for the home team as they started that possession on the 20 yard line and Kansas put no points on the board. Illinois went on to score their lone offensive touchdown on that muffed punt touchback drive.