I think the turning point of the match was 2 games all 30-40, 5th set when federar served an ace to make it deuce. Nadal never played anywhere near to the level he was playing before that.
As i wrote 4 games before that, it was Nadal's match all the way at that time. Nadal was winning to love or to 15 while federer was being stretched to deuces. Nadal had his chances and he screwed them up. I mean 15-40 two times in fifth set, you just have to convert. Especially the first time at 1-1 when federer wasn't even serving the aces.
Federer is being humble when he said he got lucky. There is no luck. For starters Federer didn't play to his level today. Nadal is no match for him on grass when he is playing at his best(federer i mean) and the very fact it got stretched to 5 proves that(the fourth set eg, it didn't even look like federer was playing). Then in the 5th set Nadal should have won it seeing how bad Federer was playing

and he didn't grab the chances he got.
In the end Federer found his game and it the champion that he is, he wrapped it up pretty quickly.
Federer should have lost today once it got to 5th set, but Nadal can only blame himself. On Nadal's side, as Vijay Amritraj said, In french open, while Nadal won comprehensively, in wimbledon, the revenge match, federer's win was anything but comprehensive.