They were a better team, period, on both sides of the ball. Arizona found its timely mojo in the 2nd and 3rd weekends of the NCAAT in a way that other teams simply did not.
Arizona, frankly, hadn't looked good all season long. On paper they figured to be a top-10 team (ranked #7 AP preseason) but they struggled to jell all season, skating by largely on their defense and looking often disjointed and lackluster on offense, right on through the Pac-12 tournament, where they were beaten soundly by UCLA in the semifinals.
So if being in the Pac-12 gave AZ an advantage in the NCAAT, why didn't it also help the team that dismantled AZ in the P12 tournament? After its run to the Pac-12 final, UCLA dropped a clunker in round 2 to Texas.