I don't know what series you were watching, but the Flyers didn't play better all series. What they did do, was they managed to capitalize on most of their scoring chances, something that Montreal couldn't seem to do. That's what was so frustrating as a Habs fan watching this series. I lost track of the number of times that the Habs had 2-3 solid minutes of puck control in the Flyers end only to have Biron make a great save and get it out to a Flyer and then they would go in and score on the rush.
The Flyers were badly outshot and outchanced all series long, but because Montreal couldn't bury their chances when they had them, the lost the series. Part of the problem was that they were letting Biron see just about everything, but even when they had him clearly beaten they would fan on the shot, or miss the open net completely.