Think about it this way: the entire offense was anemic, every opponet knew that Cooney was the designated shooter, and we lacked the low post scoring needed to keep defenses honest. When you are facing a stagnant offense, you can scheme to take things away, because the risk of someone else burning you isn't as high. Durinig the outstanding 2012 season, teams couldn't do that as easily. If you entered a game with the plan to try to take away a Triche or Joseph [or insert player of your choice here], then Scoop, Dion, Fair, Southerland, etc. all had the capabilitiy of stepping up and picking up the slack. But when an offense is so below average, you can go all out in an attempt to overplay an individual player without having to fear that others will rise to the occasion. Uconn used to do that to us all the time with GMac--overplay him and run several guards out there to make it impossible for him to get clean looks, and take your chances with the rest of the team not being able to beat you. We got them a few times [especially in the BET], but they used that gimmick defense to devastating effect several times.
So that was one factor. Another is that Cooney was a first time starter, playing his first extended dose of minutes. He is no longer an inexperienced player, and I'd expect him to demonstrate an expanded game this year, be in better "game" shape in terms of his legs, etc. as a function of having gone through the crucible last year. Demonstrating the ability to put the ball on the floor if people come charging at him would also make him more difficult to defend. He's done that intermittently, but not consistently [even though I believe he can].
So in my mind, it's a combination of factors. The entire team played poorly down the stretch after the 25-0 start [I think we went something like 4-6 from that point]. The entire offense seemed to go in the tank; Cooney was a contributing element to that, but not the main cause. Our strange isolation offense that we used last year [compared to most other years] slowed the pace down quite a bit compared to what we're used to. Cooney himself was inconsistent. And teams schemed to take him away, because they didn't fear the others' ability to compensate. We didn't have solid complimentary shooting [yes, Ennis and Fair could make them, too] and we didn't have a low post game that other teams feared; when defenses have to collapse on a good inside scorer, it ratchets up the number of kick out opportunities, gives the shooter space to square up, etc.