This trade is a really impressive course in asset management by a budget team.
The real money salary moved out in this deal is roughly the same as the salary moved in with the Trouba deal. Both Trouba and Fowler are different players, but it's close enough to a lateral move on the ice for a team that is just concerned with getting out of this season alive and needs a defenseman who can eat up minutes.
So if they are a budget team, and they weren't going to acquire Trouba without having an avenue to move Fowler, they cancel each other out. Essentially, the Ducks traded two 4ths for a 2nd to end up in a similar spot to where they would be anyways.
Then you factor in that Trouba has significantly less trade protection than Fowler. Trouba is not the player he was thought to be 5-10 years ago, but with salary retention or the Ducks taking back a contract, they will absolutely get another asset for him either in the summer or at the 2026 TDL. That might not have been the case with Fowler, because his list was so limited. Even so, they basically double-dipped by getting an asset for Fowler now, and then opening themselves up to flip his lateral replacement for another asset.