Kings traded for Lias Andersson last season for a 2nd rounder, and he ended the season playing on the second line with Vilardi (where he finally started to look good). Why would they trade him at a loss?

Wrong salary going to Buff from LV.
Would be Karlsson or Marchesault subbed in for Tuch
And of course 1 less 1st. Or no Krebs.

Or you maybe sub in Smith for Tuch and keep the 2nd 1st since they're so late. Either way, you're right.

The trouble with your idea is both Marchessault and Karlsson have no trade clauses, so good luck convincing either one of them to go to Buffalo. Tuch doesn’t have one, and he also feels I need that Buffalo has. That said, if you can convince Karlsson to come to Buffalo he’s the guy I want even more than Tuch.

I personally would decline as the isles. Mdc while he will never live up to 5 OA he rn is a solid depth player who does exactly what you want from someone like that. He gets to pucks really well, and does whatevers asked of him. He also fits perfectly in terms of the islanders running 4 lines and trotz not liking to start shuffling all his lines in case of injury, as he can sub in on all 4 lines (unlike say leo).

I find the proposed trade fair, or possibly a good steal for the Knights. As good as Tuch is, and the upsides of Glass and Krebs, they would receive a top 10 center in the league. And it would fill the biggest, and most prominent hole they have. If I were Buffalo, I wouldn't even begin to talk about a trade without two first round picks, ESPECIALLY if they're as late as the Vegas picks are/will be.

Because it's doubtful at best he's an important piece with Arvidsson, Kaliyev, and others coming

They both havea NMC Marchesaultalready said no to a trade to Buffalo a few years ago.

I can understand that, and actually would have agreed with you. But I guess Jim Fox (Kings color commenter) and others connected to the staff indicated they have plans on keeping and using Lias Andersson long term. It is expected the Kings protect him. I have to admit when he is paired with playmaking centers he looks night and day better. He has to be played with Vilardi or Byfield to be effective.