The better team won. I think Grubauer's bad play (compared to Fleury) demoralised the Avs a bit. They are a young team - under pressure they start to break, lose cohesion and stop playing as a unit anyways - they really don't need a bad goal let in, as they would have problems keeping their act together anyways.
Kadri missing didn't help team play for the reasons stated (having Kadri would have helped the team with the players in new roles problem). However Kadri has been such a hothead that I am not sure if he would have managed to help the Avs with the cohesion problem. He has lots of individual skills and nastiness needed, but can he keep playing for the team, when he gets steaming? If he had played, would he have taken a dumb penalty at the wrong time, or started playing as an individual instead of a team member, or mouthing off in the wrong way in the locker room? I think the Avs might have to dump him. He still seems to be too much of a question mark. If the Avs get a bit better goal tending, one solid, big reliable defenseman, that's all they need. They might win a cup in the next few years. Can they risk a center getting a suspension every series?