(1) health - last season he had two major injuries to his wrist and groin, causing his jumpshot to leave him completely half the season and resulting in his worst field goal percentage for a season since his rookie season
(2) the Olympics kept him motivated and in shape this offseason
(3) and mainly, Woodson changed the entire identity of the Knicks to an effective gritty passionate defensive unit. Melos played MVP level two way (offense and defense) basketball since the coaching change (if you recall Melo was player of the month last April)
The guy is literally at the peak of his prime right now, 28 years old, give or take a year is what many consider an athlete's peak.
That window of opportunity to cement some sort of legacy is small, so it's good to finally see the commitment we've all been waiting to see. Long way to go this season, and of course the playoffs, but Knicks fans should rightly be excited.
Carmelo has waited too long to truly get serious. I thought I was the only person that thought he was in poor shape compared to Lebron despite having a similar body type. He has been a "pretty-boy jump shooter" his whole NBA career.
Since The Durantula came into the league Lebron has moved on from his Melo rivalry.