I wouldn't pick just one, more realistic to rank in order.
1. Defense.
2. Perimeter shooting.
3. Continuing to be one of the best offensive rebounding teams in the country.
The single biggest trend was playing better defense, outside the CU game. We really didn't play well vs CU, but managed the win which got things going. But the efficiency on defense and eFG% the last 4 games has been solid.
Then we have shot the ball. But really, overall (outside of NU and OU) we haven't had much better offensive numbers. But, shooting better from the perimeter doesn't completely show up in there.
But in addition to these 2 major improvements, the fact that this team flat gets after the offensive glass is huge. We aren't a pretty offensive team overall and won't be, but getting those extra possessions b/c of how we hit the offensive glass gives us a bit more room for error. Absolutely huge part of the success for this team; granted not enough on its own, but still can't be discounted.