The effort level was the difference. The Avs looked like a team on a mission and fought until the final buzzer against the Predators, whereas they looked defeated after the Wild's 2nd goal.
I think the effort level was still there in the 2nd. What I think happened with regard to the motivation was Kerfoot took his bad hooking penalty about six minutes into the 2nd period. Cole took his silly holding penalty about a minute later, and Minny scored about 30 seconds after on the 5 on 3. So they still had another 1:30 or so to kill on the other penalty. After that sequence of events there was a bit of a momentum shift.
Then about three and half minutes later Barrie took his double minor high sticking penalty, so they had to spend another four minutes killing that off. Another big momentum shift. Then they gave up the back breaking 4-2 goal late in the period when everyone was caught puck watching below the goal line.
Then in the 3rd they took two more penalties and gave up another 5 on 3 goal around 8 minutes into the period.
They didn't spend all that time killing penalties against Nashville. They had turnover problems but not bad penalty problems. They had to kill three 5 on 4 penalties for a total of 6 minutes against the Preds. In the Wild game they took six penalties. 9:22 of 5 on 4 and then 0:56 of 5 on 3 which gave up two goals.
All that PK time and the two goals in the second period, especially the one at the end, sapped their momentum. The game felt all but over at that point.