I said in the summer that the Leafs would regret spending all that money on a redundant center, a position that they absolutely did not need any help at whatsoever, instead of on the blueline.
Nothing has changed my mind about that mistake since then.
It still wouldn't have been a bad thing to get Tavares for free. It could have allowed them to trade one of Matthews or Marner for an absolute haul (or a #1 D), and then sign the other to an 8 year deal.
The problem with adding Tavares and keeping everybody is that it shortened the Leafs window and completely destroyed their salary structure. Matthews wasn't going to take less than Tavares, and if they signed Matthews to an 8 year deal, they'd be spending more cap on Matthews in the short term in order to have him cheaper during the back half of the deal when the salary cap has risen. Tavares won't be around or will be in a decline during the back half, so it makes sense to take the cap savings now.
One of the biggest mistakes TOR made was not locking down Matthews in the summer. He apparently wanted something in the 12M range over 8 years. If they turned that down, and then held strong later in the season, ok sure - but it makes no sense to me that they weren't ready to do that in the summer, and then in season they caved and signed him to 5 years at over 11 million. His market value did go up in that time, but it is a very inconsistent approach.
I think if the Leafs don't win a cup with this roster over the next 5 years, all the analysts and historians will point out the Tavares signing as being some trojan horse that destroyed the Leafs by making their salary cap situation unsolvable, but I still think it wasn't so much the Tavares signing as it was botching the extension for Matthews. Had they signed Matthews at 8 years 12.34 in the summer, while it would not have been a home run deal, it would be significantly better than paying him a few 100k less and only getting 5 years of term. It would have also set up Marner to take a similar deal, and assuming they are prepared to flip Nylander for someone like Pesce, they would have been fine cap wise even with Tavares/Marner/Matthews eating up 36 million.