why? what does this do for the Rangers?

Trouba contract is going to be a huge long-term problem for the rangers. Devils trade gives them significant cap flexibility and a couple decent players. montreal trade is just for fun

This does nothing to improve the Rangers.
You can say bye bye to Kakko because someone will offer sheet him with absolutely no hesitation.
Strome will be getting between 5.5m to 6m per year.

I would rather package LAF in a deal for the 1OA

Which is exactly why the Devils say F*ck you and then hang up the phone

Devils would rather keep Zacha and Severson.
Also, Zacha's next contact will be $4.5-5 million range. Severson in $5-6 million range.
So I am not sure it saves a lot of $$, if that was the goal here.

Trouba and his contract aren't really an issue.
he has put the team on his back, emerged as a leader and is starting to put up some points.
sure he isn't as flashy as he was with the Jets, but he doesn't have to be.

the above moves don't really make the team better.
if teams like Tampa, Vegas and Toronto can work the cap year in and year out, the Rangers will certainly be able to do the same.

Not a chance Devils do that
I rather have Severson over Trouba
And Zacha over Kravtsov

Yuk overpaying Severson 6m and Zacha 5m is not appealing, wise or possible. Besides the fact that Trouba is in beast mode (like others, yes thanks to Reaves) and after 24 season will be available @ 2x4m which should fetch a pretty penny.