On one hand, Montreal has been red hot of late and they very well may have their goalie of the future. They did a great job of boxing the Avs out and have enough speed and depth in their lineup to make it really hard for Colorado to do what they like to do, doesn't help that all the guys who are capable of scoring garbage goals (apart from Lehkonen that is) aren't in the lineup.
On the other hand, Avs as a whole just up and decided to play perimeter hockey and eventually, Montreal broke through. As others have already said repeatedly, it was a trap game.