I believe it was GSP (paraphrasing here) that said when you lose your Achilles fist (I think that's what he called it) you are mentally broken. The Brock that came in and destroyed people, took a beating from Carwin then jumped up on the cage and hit himself in the face to prove he can take a punch, that guy was gone ever since the Carwin fight.
That disease took his strength both mentally and physically, when you don't have that feeling of physical superiority anymore the entire game is changed. Brock had the potential to be a wrecking machine because few people could stop his takedown when he was determined, but once he got sick he lost his determination. I can understand that, however it's all because he ate a meat only diet, why nobody helped him out and corrected that boggles my mind. A world of potential down the drain because he wouldn't eat right.