Tanner Pearson is useful player. The Canucks traded him after his signing bonus and sent a 3rd the other way. He was traded, because the Canucks needed a goalie.
Beauvillier was an established NHLer, on an expiring contract, who had 28 points in 55 games for the Canucks, but had a history of strong play on the islanders.
Pearson when the Canucks moved him, was absolutely cooked and pretty much everybody knew it. He'd had about eleventy billion surgeries on his hand and was at the age where slow players get even slower. Especially with huge amounts of time missed in the previous seasons due to injury and not even being able to really consistently train and keep himself in shape.
He had like three good games with the Habs and then became utterly useless dead weight.
Beauvillier also had a history of being "streaky" and putting up points in a top-6 role for a little while, which he did upon arriving with the Canucks...but then did exactly what he's always done, and completely disappeared.
But there is a fair point in there about Ruthervin managing to actually unload some of these guys without "paying" by just being patient and waiting. I think Desharnais deal is within the scope of players who could be attractive enough at that price to certain "rebuilding" type teams. He's still a huge, physical RHD who is by all accounts, a really solid hard working professional and great teammate.
So here's hoping...But to me, it seems more likely to be a part of some other deal as basically a bunch of cap going back the other way on a more expensive, much better defenceman.