There's a number of things that could explain his fall: he's getting older, his passion for the game and willingness to prove himself game-in game-out is probably not the same as it was 5 years ago, he is a dad now, he's also probably still trying to find ways to cope with the extra responsibilities of being the team's captain. He has made a very comfortable living and is guaranteed to see that continue, and so it becomes a matter of perspective. Does he want to risk as much shift-to-shift as he did a couple of years ago? If his on-ice performance in the last 2 years is any indication it's pretty clear in what direction the answer lies.
We are rabid fans and expect the players to have the same zeal, but at the end of the day this is just a job for them and age probably makes that all the more clearer. I can see a similar thing happening with Price, he signed that contract knowing full well that it would probably cut his prime in half and lead to a pretty toxic relationship with the fans at the Bell Centre in the coming years; but will any of that matter when he's 40 and sitting on a fortune of over 84 million dollars?