Trouba manufactured his way specifically to NY so his wife could continue to pursue her medical education. He then signed a long term contract with a NMC. So this alone makes this trade an non-starter. I could see Trouba agreeing to go to another major US city at some point, but there was something about certification or licensing for his wife's medical training (sorry not sure what she is studying) that was the driving reason to leave Canada.
Secondly, Trouba is exactly the type of RHD I would like to try with Hughes, but $8 for this and the next 4 seasons, when you're already paying for Hughes, OEL and Myers (I know Myers is in the deal, so his cap would hypothetically be gone) big time $$ it isn't reasonable to add another long term high priced contract.
Finally, losing Boeser, Hamonic and Myers and adding only Trouba wouldn't improve this team. It would improve our top pairing and solve one problem but it would open up depth issues at other positions. I get that these other issues could be addressed other ways, but it causes a trickle down that would definitely have a negative impact on the team.