The Leafs did announce they'd blow it all up and rebuild from scratch. They predicted it would take up to five years to be competitive. Turns out they were wrong and it took two years. But this was because they lucked out and wound up being able to draft a hockey prodigy in Auston Mathews. It also helped that they also had the likes of Morgan Rielly, William Nylander and Mitchell Marner ready to contribute a the time Mathews first stepped onto the ice.
The Edmonton Oilers never announced a rebuild. They kept finishing last or close to it and wound up drafting #1 year after year. They had become a joke. But Bob Nicholson, Peter Chiarelli and Todd McLellan were hired and they finally had a competent management team. They got a very promising goalie in Cam Talbot from the Rangers and then got lucky by being able to draft a generational player like Connor McDavid and suddenly their future looks promising. Now they can continue building around McDavid but for myself the new management team had as much to do with their recent success.
Other teams were fortunate to be able to draft high-end talent on which they could build their team around. Pittsburgh was on the verge of losing the Penguins when Mario Lemieux was drafted back in 1984. The team had alerady previously filed for bankruptcy and at the time of Lemieux's arrival were still experiencing financial problems, the building was half empty game after game and they sucked on the ice. But Lemieux's arrival changed all that and the rest is history. The same scenario occurred 20 years later when the team was almost sold to Jim Balsilie who wanted to move the team to Hamilton. But the Penguins lucked out and won the draft lottery in 2005, drafting Sidney Crosby (another generation player) ahead of Anaheim who wound up having to draft Bobby Ryan instead. The Igloo suddenly filled up again, the team starting making money and along with the likes of Crosby, Geno Malkin, M-A Fleury and others became competitive and won a few Cups.
Chicago was going nowhere until they wound up drafting and acquiring the likes of Patrick Kaine (#1 overall), Dustin Keith, Jonathan Toews, Dustin Byfuglien, Patrick Sharp and others.
The problem with the habs is that i doubt the fans will agree to put up with a total rebuild like other teams did. The fans and the media will find it unacceptable that the Montreal Canadiens become the worst team in hockey. They did get lucky a few times over the years by positioning themselves to draft the likes of Carey Price (#5 overall) and Alex Galchenyuk (#3 overall) and drafting PK Subban in the 2nd round (43rd overall). Who could have predicted he'd still be available when it came time for the habs to draft in the 43rd position?
I think it was a mistake to extend Carey Price's contract during the offseason. His contract may very well become an albatross. Trading him before his current contract expires may have brought back the players they need in order to be truly competitive. Charlie Lingren would have been able to come in and fill in for Price's departure. Or maybe Zachary Fuchale. Look, the habs aren't going anywhere anyway with Price between the pipes for years to come. So why not roll the dice and try to acquire a few top players and prospects (plus high draft picks) by trading Price? It worked for the Quebec Nordiques/Colorado Avalanche when they traded Eric Lindros to the Flyers. It worked for the Dallas Cowboys when they traded Herschel Walker to the Vikings. Why couldn't it work for the habs?