I think Gomi mentally just burnt himself out and never came back with the same poise.
He's not like some other legends who've declined due to aging or serious injury. Gomi, like Penn has stayed healthy as a horse (prior to breaking his hand recently, that's first notable injury I think he's had in his career and he should be fine with something like that) his entire career. His body has been knock on wood for years. It's mental for Gomi I think. He's gotta be able to have that fire in his training. I mean he's not getting any younger but most of problems I believe are behind the scenes/in regards to his camp. I mean there was talk that Gomi at one point was just training with high school wrestlers in Japan for his fights.