It was incredibly stupid of them to go after Tavares. I know he was UFA and essentially "free," but in reality, it cost them the opportunity under the salary cap to get a good defenseman to fix their blueline. And I absolutely guarantee it ruffled the feathers of the dynasty kiddie trio for the leafs to bring in a "savior" like that when they were supposed to be the focus of the club. There is too much ego, and not enough blue collar on that team.
I don't agree with this logic, because going after Tavares gave them an elite C for nothing but cap space. They could have turned around and traded Marner or Matthews for a top young defenseman and still been ahead. It also theoretically should have set an internal cap ceiling. If Tavares came over as a UFA for 11 and he and Matthews are in the same tier, Matthews should have been in a more difficult position to bargain for more than 11 on a 7 year term.
The biggest mistake they made was mishandling the Matthews extension. They made a franchise altering mistake with how they handled it. They apparently could have had him for 8 years at around 12 million or so in the summer of 2018. While I understand them saying no, saying no made absolutely no sense if they were just going to cave and end up signing him to a million or so less without the full term.
The consequences to the 5 year deal are huge. It set a much higher ceiling for Marner. It also means that their RFAs are not signed long enough to have the cap deflate their hits. By the time the cap ceiling goes up enough to give the Leafs room to build around those contracts more effectively, they will be almost done. The Leafs won't benefit from the second half deflation of the contracts the same way a team like Edmonton is going to with Draisaitl and McDavid making 21 million combined.