Injuries and fitness killed his career. I remember when he and Neymar where "next up" for Brazil. Neymar lived up to his hype and billing, Ganso just didn't. I remember he was at Sevilla a while back but it just never got to work for him.
Yeah, the knee injury he had towards the end of his time at Santos really hurt him. He was never an explosive athlete, but after that he clearly lost a step. And he was always a guy that needed to have the perfect system and players around him to thrive. Without those things in place he struggled.
Even early in his time at São Paulo he looked washed, until they surrounded him with top level players like Pato and Kaká and brought in Ramalho who managed him at Santos when we won the Libertadores. He was never going to have that type of picture perfect scenario in Europe.