Not allowing cu to penetrate kept them off the ft linte, which as you point out made the difference. We should copy that against good driving teams 
CU going to the FT line wasn't a big problem for us, they had 11 of their 27 attempts in the last minute and a half of the game when we had to foul. The problem with FTs that was we didn't draw enough fouls, especially after we had them in the bonus by the 14 minute mark of the 2nd half. We only had 16 FT attempts and as a result we only had a FT rate of 24% (compared to CU's 54%), well below our season average. Then we got beat on OR% 39.1% to 36.6%. And the 64% eFG% we allowed when we only had 47.7% ourselves ended up killing us.
CU still out-shot KU by a small margin, but b/c KU has a 20%+ advantage on OR% and a 30%+ advantage on FT rate; that more than made up for letting CU shoot pretty well. Though the 64% eFG% we allowed is terrible, even against a good offensive team like CU.