Each and every one of the players (and coach) listed have something to do with the Bruins' resurgence, but the key factor isn't even on the list, and that's the return (healthy) of Patrice Bergeron, allowing Boston to have two top notch offensive lines instead of only relying on Savard's.
I'd go further by saying that replacing Murray's old legs with Ryder was also a contributing factor.
In my eyes, its the emergence of our young talent - Kessel, Krejci, Lucic, Wheeler, and Hunwick. Kessel is turning into a superstar, and is our leading goal-scorer by far. He's found amazing chemistry with Savard and Lucic on the first line. Besides Lucic's success on the first line, he is a force in other aspects of the game. He's emerging into a top power-forward. Krejci is one of our all-around best players and his hockey sense is phenomenal. We didn't expect Wheeler to play much this to this point in the NHL, but he's put up 9 goals so far, and has found some great chemistry on a line with Ryder and Krejci. Hunwick was called up to fill in on D, and he's turned into arguably our best offensive defenseman (besides Wideman).
The Bruins are a good story. Lots of highly skilled youth beginning to emerge, plus solid goaltending. The big question for this season is will the youth stay consistent enough to make a long run, but for the long term, it looks like the Bruins ought to be a contender for a while.
I don't understand how Thomas is winning this (as of now). Fernandez has 9 of the Bruins' 21 wins ... Thomas is playing well, but has only factored in 12 wins so far.
I voted Julien. He identified what lines weren't working and changed them up, creating two lines that are scoring at a very good pace, and he's done a great job of juggling two goalies that are both playing like #1s. Julien is who I credit the team's success to.