Congrats to Stan. it's insane that he has now won 3 out of 4 slams. That's incredible and nobody could have predicted that.
However, I actually didn't think this was a typical case of him being on fire to where there was nothing Novak can do (like say, the FO final last year). I actually thought that while he played well, Stan didn't red-line his game, which is what you think would have needed to happen for him to beat Novak. In a way, that's just as impressive, and a sign of him becoming truly elite, as he's not someone who needs to have an unusually hot day to win.
But, when you look at how he was hitting his groundies, you can see something is a touch off. The forehand in particular, lacked direction. You could see so many instances where it looked like he had a forehand lined up down the line, and he hit it almost to the middle. He has enough power and depth to where it ends up being a really good rally shot, but those are the kind of shots he would normally convert for a clean winner. The backhand wasn't as hot as it normally can get either, and you can visibly see him holding back a bit on some mid court backhands that he would usually destroy because he wasn't completely feeling it.
Of course, I'm nit-picking, as you could also spot some insane winners that he hit. But the reason I bring this up is two-fold:
1) Stan played a smart match and wasn't in pure shotmaking mode. Specifically, his usage of the cross court sliced backhand to Novak's own backhand, knowing that Novak just doesn't muster up quality replies to that shot. It's something Federer has had success with in the past against Novak, and even Del Potro recently.
2) Novak was really disappointing in his tactical approach and his inability to adapt. He let Stan get away with way too many harmless chipped backhand returns, and instead of punishing them by running around his backhand (something Federer and Nadal do better than anyone. They destroy the slice), he just pushed the ball back with a cross court backhand and the rallies were basically neutralized, which as a server, is not what you're typically looking for.
Another thing that stands out to me is that Novak, despite having so much success against Stan historically (as in their overall h2h), gets really tentative when Stan plays well in these big matches. He finds it easier to defend out of his mind and hit incredible shots from unlikely positions (and he didn't do enough of that last night) than to actually take control of the point and move Stan around, which is what he normally does so well. Part of it I think has to do with intimidation. I really think Stan's game intimidates Novak when he finds his groove, especially Stan's own ability to hit some insanely powerful shots even when it looks like Novak has the ascendancy in the rallies. Novak is a bit afraid to fight fire with fire with Stan as he believes that's Stan's game. That's understandable, but Novak's inability to come up with an alternative isn't.