two problems here. 1st it assumes you can put Kesler on LTIR.
2nd is that the ask on Marleau was a younger player. aka prospect. To take him. This is assuming he's a LTIR and not active roster.
While you can look at it as a cap swap, it's not. If Kesler is going to LTIR, they still get the cap space. Much like why you traded for him. and that has value as opposed to eating away at the cap.

And they have nathan horton who is already on ltir! Ltir can bee use to buried bad contract! It just too gave you marge for signing players and bonuses. You should try too explain that too BurgerBoss

True, to the first. They will get two 4th round picks plus Marleau for eating a bit of cap and helping the Leafs. Ducks are rebuilding and are likely not going to spend to the cap. Anaheim is also in Cali which is where Marleau likely wants to go. I doubt they will put him on LTIR. Marleau's contract is up next summer though unlike Kesler's.

The problem here is that his cap space is worth more than 2 4th round picks that have like an 8% chance of turning into a player.
Which is why the ask on Marleau has been a younger player. It's not that teams can't take him. They can, they have talked about it. The issue is the ask. No one is giving up that cap space for basically nothing.
Pure cap dumps for low round picks are rare. You got to give to get. The player has to at least be able to contribute. But at Marleau's age he's a pure cap dump.
The real deal is Kesler, it's a big assumption he just tales LTIR and the league OK's it. If that's the case, why would ANA even bother. I'm sure there are a lot of other teams that would offer up on that if that was the case too.

So it would require higher picks and or a promising AHL player/NHL Roster player? I think you are right.

Mayfield for Zaitsev literally makes 0 sense. Why would the isles give up a better, younger, and cheaper RHD for a crappy, older, more expensive RHD one for one???

Because Lou is GM

That makes literally no sense