Can you provide links to these predictions calling for Ottawa to win?
Bleacher Report had Ottawa at 25-1 for winning the Cup and Montreal a 16-1.
Hockey-Reference had Montreal at a 6% chance to win the Cup and Ottawa at only 3.8%
The Washington Post, while calling Ottawa the best bet for an upset, also only gave them a 45.5% chance of winning the series, obviously meaning the Habs were still the favorite.
Puck Daddy had Montreal at 10 to 1 to win the Cup and Ottawa at 18 to 1.
So yeah, not really sure where you got the impression that we were the acknowledged underdogs from.
http://hfboards.mandatory.com/showthread.php?t=1875071&highlight=predictions
More analysts picked the Sens to win the series