Chapman is also like, top 1/2 at his role. While trading Torres for him is still pretty stupid there's very few players of his calibre available when you're 100% going for it. The Cubs were the best team in baseball with an average-ish to below bullpen and had a chance to break the infamous curse by adding the best possible upgrade they could acquire. The White Sox are not close to being the best and just traded a promising MLB ready SP with control for one who might give them a 2 win upgrade as a rental while the team still has other holes.
The White Sox could just as easily have signed Bauer, an actual potential top 5 SP while giving up no assets.