Coming into the game, KU's offense was scoring about 35 ppg in conference. They scored 21 against ISU.
Coming into the game KU's defense was giving up about 32 ppg in conference. ISU's offense scored 21 against KU.
I know...the ISU defense often doesn't look good because they give up those 3rd/4th and longs, and it would be very helpful if they could clean that up. But the bottom line is that although the defense was not stellar, they did good enough to win. Stinky, unimaginative offense lost the KU game.
The 3rd and 4th down conversions have been an achilles heel for a long while now and aside from the score can be the 'margins' aspect between winning and losing.
It's like if a basketball defense guards well overall and disrupts an offense but gives up boards/putbacks.