He suffered head trauma and dental damage. That isn't something you just bounce back from. Yeah he had some good results afterwards but I've personally always thought something looked off about him subsequently. That said Spence has had a very good career. I don't think he was ever a generational talent even before the accident. Just a really good, well rounded and tough boxer. He was definitely world class but not a Mayweather or Crawford type talent. In saying that very few fighters are.
He has his health and hasnt frittered all his money away so it seems. If its true he doesnt really like boxing he's done pretty well out of his career in my book