I give Bergevin no slack at all but I think I'd give him a pass on this one. I don't know if I'd read/heard that MB absolutely would not go 2 years on Perry but given what he signed for I can't imagine there would be any difficulty giving Perry an extra year when the AAV is in the 1M range. If Perry falls off the cliff you just bury the salary in the minors, no biggie. Considering he handed out extensions like candy to supplementary players like Byron and Armia at much higher AAV I cannot imagine the team wouldn't go 2 x 1M or so for Perry.
I don't think any of us expected last place but most of the people here predicted Montreal would be in tough to make the playoffs. I presume the players would also have a sense of where the team was at. Perry wants a Cup, if I were him, given roughly equal offers, I'd choose Tampa over Montreal too, and the most logical explanation IMO is just that.