He's an author, not a game dev. The game devs licensed his IP. All of this is explained in the article.
You might also be surprised to learn that Andrei Tarkovsky, director of the film Stalker (1979), didn't personally learn C++ and program S.T.A.L.K.E.R. (2007). Neither did Arkady and Boris Strugatsky who wrote the novel Roadside Picnic (1971) that all of these works, including Metro, are inspired by.
You might also be surprised to learn that Andrei Tarkovsky, director of the film Stalker (1979), didn't personally learn C++ and program S.T.A.L.K.E.R. (2007). Neither did Arkady and Boris Strugatsky who wrote the novel Roadside Picnic (1971) that all of these works, including Metro, are inspired by.