Surely Nadal did not play as well as he has in the past or will in the future. But that's just part of the game. If Nadal was able to play at 100% of his ability every time he stepped foot on a court, then maybe he'd be the GOAT one day. But the truth is nobody can sustain that level of play because it takes its tool on a player.
Fed's consistency over the years in staying injury free and playing at a top level most of the time has far outpaced Nadal, which is why Fed's stats are so incredible. Too many people have short memories and think one match tells you how the player is going to play in every tournament thereafter. This is a good victory for Fed, but it doesn't mean Nadal won't bounce back at the AO better than we've ever seen.