I'm just reading the comments and I'm just sighing and shaking my head at how little people paid attention to the first chapter. He dedicated his life work to researching and building magical knowledge that could be useful for everyone. This future, everything he ever worked on and for has crumbled into loose stones. There is literally nothing for him to learn, teach or research because that foundation isn't even there. He can't learn anything because this is all basic magic for him, he can't research because he would just be rediscovering stuff he already knows, and attempting to teach would require rebuilding the foundation of the magical system itself. It would be an entire generation before he can advance magic again and that would just lead to him repeating the same mistakes as the past.