He wasn't trying to win. If he DID win, his whole plan would have been ruined. That being said, he was also clearly weak from old age. It could have been a little more of an engaging fight, but I enjoyed it nonetheless. His focus on using powerful magic was cool, and made sense since physically he wasn't at his strongest. I was a little disappointed by the music, it's probably my least favorite boss theme in the series. They should have stuck with some version of Fate of the Unknown, from the Secret Ending. Knowing that he's the main antagonist, I think of it as more of a preview than an actual fight. I'm sure we'll get a better challenge out of old man Xehanort in the future.