Yeah I think the main argument for Bellinger is that, mainly given the current roster makeup, Bellinger represents the best use of $150m-$200m, with the secondary argument being that a PCA trade opens up the potential options significantly.
The team needs offense. PCAs like, 90% ceiling is probably a center field Hoerner, so even in the best of outcomes you're still looking at another glove first guy. A very valuable glove first guy, to be clear, but you're really starting to test the limits of how you want to get to that 40-45 fWAR number. We need to figure out a way to find an offensive upgrade, but he can't play short, second, left, or right. You aren't going to pay a first baseman $200m (because, in my opinion, using Freeman and Olson's contracts as benchmarks, there are no $200m first basemen available), the best third baseman upgrade is a glove first guy not worth that kind of money, the only real DH option went to the Dodgers, and catcher there's obviously nothing. Bellinger represents premium offensive production relative to centerfielders. And PCA represents maybe the most valuable trade chip out there for a team looking to rebuild, cut costs, etc.