TDL

Why would the Islanders downgrade a draft pick and take Dermott when they can just get a late pick for Chara? Dermott isn't improving the Islanders defense.

I think the Leafs want to upgrade their roster at the TDL, not downgrade

Watch the highlights of the Flames/Sabre game. https://www.nhl.com/video/buf--cgy/t-277350912/c-10997050
Then watch the highlights of the Leafs/Coyotes game. https://www.nhl.com/video/ari--tor/t-277350912/c-10878724
Mrázek has allowed 17 goals his last 3 and half games, 4.85 GA
Try real hard to convince your self that Dustin would be a down grade over Petr.
Just taking Mrázek's contract would cost more than a second, adding Dustin more again.

Crouse is Kadri lite, and for a second would be a good add on.
Chara adds the playoff experience and leadership that appears to be lacking, for Dermott who is absolutely the worse of all Leaf defensemen.
I have not checked for this post but last week Dermott has the lowest ice time, no PP, low PK, lowest hits, lowest Blocked shots, fewest goal, fewest points of any TML D-man.
No one will give up a anything for him.

I do not know enough of the Flyer trade, but you could be correct as Kerfoot seems to be the whipping boy of the Leaf fans.
Maybe they expected him to be producing as if he was Kadri's replacement.

@TheWomper
But Tokarski, Chara and Crouse are all upgrades.

This is such a weird argument but you did a great job of breaking down your points so I'll break mine down the same.

1) You can't talk about Chara having playoff experience as a 3rd pairing defenseman and then argue that Tokarski's 68 game NHL career with 0 playoff games is somehow more reliable Mrazek's almost 300 game sample size with playoff experience on top of that. Yeah Mrazek is having a bad season, but I'll take the playoff experienced goalie with a better career over a guy with a 0.905 SV% and 3+ GAA.

2) I agree that Crouse is a good add to a team that needs this type of player, but he's an RFA that the Leafs most likely will not be able to pay and Arizona is going to want more than a 2nd for him.

3) Dermott is a 6th/7th guy. Of course he has the lowest blocked shots, goals (which, who even cares?), and points. He's here to replace others for days off and injuries. I can see him being moved, but the Leafs need to address a Muzzin replacement for the time being and IMO Chara isn't it. (I am willing to admit that I may be off with this point and an extra defenseman like Chara may be what they need, but it's hard to argue that this will make the Leafs 'better' overall)

4) The worst point is definitely Kerfoot. We are literally giving the higher pick to receive two players of lower value. Overall just really bad on that one. Quantity does not equal quality