Interesting storyline for the brawl:
A minute or two earlier Isiah was having a conversation with melo while one of the Knicks players was at the free throw line. Based on Isiah's post game comments it seems likely that Isiah was asking Melo why he was still in the game when it was such a blowout. [We have confirmation - here is Isiah Thomas: "I just said to him, 'You know, you're up 20, you're up 19 with a minute and half to go, you and (Marcus) Camby really shouldn't be in the game right now."] Around that same time JR Smith had taken a Knick turnover and done a fancy reverse dunk, despite the fact that the right thing to do would have been to hold the ball and kill time. I think that it's possible that Isiah told his team something like, "They are trying to embarrass us here and it's uncalled for. if they try to run up the score any more, you make sure you stop them from scoring at all costs."
And it's true. It seemed like George Karl was trying to embarrass the knicks in a sort of retaliation for the way Isiah Thomas and the knicks handled Larry Brown's firing. I don't think Thomas anticipated or wanted any of this to happen, but it's possible collins came in with orders to give hard fouls. George Karl and the Nuggets paid dearly for trying to run up the score, as their two top scorers are now likely facing suspensions. Carmelo will get at least 5 and smith will probably get about 3.
It's also worth notiing, in Isiah's defense, that Collins had been called for a flagrant 1 one night earlier for a similar foul, so he may have chosen to interpret hard foul as, "throw the guy to the floor".