I don’t see why the rangers would ever do this, they lose a ton of speed in their lineup, and for the leafs they lose a ton of defensive presence

Pure fantasy, Panarin isn't going anywhere.

I don't see Tavares leaving TOR and especially not for NYR. Then I don't see Drury adding a player like Tavares either. I also don't see it being a one for one trade.

More needs to be added by TOR. I would say a prospect + 2nd maybe?

Of course not.
But through the playoffs this was an obvious weakness for NY.
Tavares(or comparable) CENTERING our 2nd would add the flexibility to use Trochek in a 3C shut down role, come playoff time.

Trading Panarin is not gonna happen, but for the sake of argument:

The only reason to trade Panarin is if the trade both:

A) Brings back a haul
B) Frees up a good chunk of cap space

This trade does neither.

Nah you're mistaken about the return.
They are win now mode.... no need to pay the salaries they have now if you're not going gor it.

This deal makes them a much more difficult playoff match up.