Who says there was terrible suffering? Modern slaughterhouses minimize this possibility (Grandin's legacy), and 'bespoke' slaughtering effectively eliminates it in my direct experience. One day it's munching away on some sweet feed and then BANG cow/pig/etc. heaven.
The same is true with ethical hunting — I'd far rather take a well-constructed bullet to the boiler room and quickly fade out than have predators ripping me up while I'm still alive.
The point of fully exploiting the carcass is recognizing that a life was taken, regardless of suffering, and choosing to make as much use of it as possible. Nothing I've written is intended to minimize suffering or other inhumane treatment.