I certainly won't argue that Drury may have had a clearer NHL path elsewhere, but I still maintain that his path with the Canes right now is very different from what Fox was looking at back then. At the time Fox made his decision, at least on paper there wasn't an even an apparent spot on the team for him, let alone as a starter. This wasn't Norris winner Adam Fox, this was a promising college player with no pro experience. On the right side the Canes had Hamilton, Faulk, Pesce, and TVR, all young, all experienced, with
3 of them being legitimate at least 2nd pair NHL defensemen.
Drury on the other hand could potentially be competing for a 4th line spot right away. Trochek's contract is up next year and depending on what happens with the a bunch of other players (Dougie, Svech, Necas, goalies) the Canes might not be able to afford to extend him (or even want to if his play regresses). Staal is going to turn 33 years old in 2 months and his contract expires the season after next; is there an opportunity in the not too distant future for someone like Drury to slide into the role Staal currently occupies when he slows down (Drury will still only be 23 yo when Stall is 35)? I agree there's a chance that Necas could at some point move back to center but if that happens I don't see Drury competing with him for the same spot (Necas 2nd line, Drury bottom 6).
As an aside: you point out that Drury's camp obviously thought that waiting around wasn't worth it. One factor that might have contributed a bit to his decision is how promising the Canes look with respect to competing for a Cup. Kid might rather have faced tougher competition to make it with a (hopefully) perennial Cup contender than an easier route with one of the leagues bottom dwellers. Don't know how many would have viewed the Canes quite in that light back in early 2019.
edit: just read this back and I'll lay off more commentary on Fox's signing for a while, lol. I've made my views known and I'm just beating a dead horse at this point. Sorry about that, folks!