Well Kim has been steadily improving as he adjusts to MLB and that lead to a 4.4 WAR age 27 season.
Manoah did the opposite as ballooned to over 320 pounds and put up a negative WAR season.
In theory, it's risky trading 4 years of Manoah but in reality the guy who was a frontline starter is probably gone. And I don't hate him like some, I think he can be serviceable moving forward but there is a chance that he's cooked. So there's risk to trading him and there is risk to not trading him while he still has value.
Plus, one year of Kim is nothing to sneeze at on its own. But he seems like the kind of 2nd tier player that Atkins could lock up to a Berrios or Springer like contract and that would allow us some flexibility with Bo who we could deal or let walk in FA.