That's true of course, but the book series wouldn't have become a cultural phenomenon that makes billions.

Unlike, for probably the only example, Harry Potter, which was already a cultural phenomenon when the first film was announced.

Yes, there was some stuff done that sold some books, and some more stuff done (under licence from the author) that sold waaaaaay more books (that goes to the author) and generates cash.

What's the problem, I suppose? The author definitely did better out of the TV production than vice versa.