I'm not sure if Laughton is a long term 3c here. Might have to force it for this playoffs and address it properly in the offseason.
Obviously, Laughton was seemingly the best centre they could get. The haul for Brock Nelson was huge, Brayden Schenn & Ryan O'Reilly didn't want to go. Cozens/Norris weren't going to work from a cap or asset standpoint, and even Coyle, the Leafs didn't really have a Mittelstadt-comparable to move.
While I'm far from happy about the fact that they gave up a 1st round pick in this deal, there is at least some logic in the totality of the Leafs deadline this year.
There's a massive amount of new money in the system next year. It's going to mean that acquiring players via free agency is going to be extremely expensive and competitive unlike we have seen in many years past.
The Leafs have $27.5m in space with 7 forwards, 7 defencemen, and 2 goalies signed. Figure Knies and Tavares at $13m between them; leaves you with $14m for 4 forwards.
With Laughton in, you at the very least have a top 9 LW, meaning your left side is set with Knies-McMann-Laughton. Maybe Marner goes and you sign Sam Bennett for $8.5m. Maybe Marner stays (in which case Laughton probably has to be a centre).
Getting 2 players with good term was pretty integral for this team. Would it have been better to do so with a 2nd and 3rd, saving the premium asset so that you have something to shop with next year? obviously.
Would it have been better to keep Grebenkin who could potentially fill a role similar to Holmberg at ELC-money? obviously... but the Leafs need to get away a bit from the concept of filling the bottom of the team with sub-$1m guys every year. The quality of those guys, especially if not ELC players, is going to fall as teams have all this extra cap space.