How did the devs manage to make this game run this terribly?

There was an issue that was going around not too long ago so you might still be encountering it. If your system is very powerful, the frame rate can start to creep up and actually cause problems. If you cap your fps at various levels, you might have a more smooth play experience. Start with 60 and see how it does. On high end systems, changing the graphics quality settings often has little to no effect on performance.