I think a bigger difference is that books are just astoundingly cheap to produce compared to TV. That gives more freedom to take risks and try a huge number of

I think a bigger difference is that books are just astoundingly cheap to produce compared to TV. That gives more freedom to take risks and try a huge number of different ideas, some of which will pay off and produce something great. For the cost of one episode of Game of Thrones, you could publish hundreds of books. Even cheap garbage like reality TV costs enough per episode to publish several books (through a real publisher, would be even more if you count self-publishing).