Andre's one of the best wind players of all time. If anything, those conditions favored him, and in fact that seemed to be the case when he won the fourth set.
But then Federer figured out that the wind was keeping Andre from hitting hard, deep, precise shots, so he started coming in behind more of the points. It was a smart move on his part. couple that with a few dumb errors from Andre
, and Fed had the fifth set.