quoipourquoi
Goaltender
Serge Savard oversaw some good drafting years in the '80s (though it's hard to know how much credit he deserves for this), but his trades were generally bad. He dismantled a very good and deep team.
The Habs defensemen in 1990 included:
Chris Chelios
Eric Desjardins
Mathieu Schneider
Petr Svoboda
Craig Ludwig
Sylvain Lefevbre
Jyrki Lumme
They could have sailed through the '90s and to the end of the DPE with this group. But they traded every single one of them, and this is the primary reason the team declined. They also traded their best young forward (LeClair), their best defensive forward (Carbonneau), and others.
The decline of the team is what led, ultimately, to the Roy trade. The team was going down with or without Roy. He was lucky to get out when he did, and obviously very lucky to be going to the best up-and-coming team in the NHL.
Patrick Roy was traded from a team - Montreal - that, months before - didn't make the playoffs with him, to a team - Colorado - that, months before, finished 2nd overall in the NHL without him.
I wouldn’t define the Montreal Canadiens’ trajectory by the lockout-shortened season. Obviously they made the playoffs in 1996, as well as 1997 and 1998 - the latter season seeing them with a GF:GA ratio of 235:208 to Colorado’s 231:205.
Even when they started missing the playoffs, it was largely because their offense cratered. The 1999-00 Montreal Canadiens were 4th in GA, so saying the change in defensive personnel is the primary reason for their decline doesn’t seem accurate.