Who really knows? We can only theorize and speculate. But it's never one single thing. It's probably a combination of a bunch of things like him hitting the mental maturity peak, and this is really the first year where he is the de facto "captain" because he is the longest-tenured player currently. No more Staal and Lundqvist, so he's got to be the man. Remember, he was a mental case for awhile, it was reported, overthinking and stuff. For the longest time, he didn't know how to play because of his strength. It's not only the 50 goals. It's noticeable how much better he is on the walls on the forecheck this year. It's like he's finally learned how to use his body effectively without overdoing it and getting called for infractions.
Or, less scientifically, sometimes it just "clicks."