Outside of the obvious (their best, Price outplaying our best, M & M) I'm still trying to figure out how Montreal won this.
Josh Anderson (you would think he was the second coming of Cam Neely the way some were talking before the series) had a great game 1, but outside of some nice hits and the odd rush, didn't do any real damage after that. Toffoli and Gallagher were almost completely ineffective until late in the series. Caufield had flashes but didn't score a goal or look that threatening most of the time. Kotkaniemi, Suzuki and Perry were good but never what you would call dominant at any point.
Our weakness was thought by many to be depth, that other than the big guys, no else could be counted on to score. But we actually did get valuable contributions from unexpected places (Spezza, Muzzin, Brodie, Kerfoot) which is what you need to win in the playoffs.
If you had been told all that before the start of the series, Montreal shouldn't have had a prayer. But they played a true team game, found a way to get timely goals and defended superbly.
Which brings us back to start. Our two biggest guns failed completely, there is no way of getting around that. They didn't have to dominate every night, but even for 2 or 3 games or large parts of games would have been enough and we wouldn't be having this conversation.