I don't really enjoy watching boxing most of the time but I enjoy watching the few fighters who actually get good at it, and Golovkin is one of the three best I've ever watched, the other two being Duran and Roy Jones.
This fight was unusually interesting. Stevens was the most dangerous opponent Golovkin had faced (only one of Stevens last four opponents had made it past the first round). Usually when you see somebody 5-7 fighting middleweight you're seeing somebody moving up one or two divisions; Stevens was actually moving DOWN. Stevens is simply that heavily built, sort of like a miniature Mike Tyson.
There was also the puncher vs counter-puncher thing and Golovkin just provided the world with a textbook on how to demolish counter-punchers.