Reminds me of when George RR Martin asked King, "How the fuck do you write so many books so fast?" https://www.youtube.com/watch?v=xR7XMkjDGw0
hilarious. But really, they dont write the same sort of books... Martins books are hella complex worlds. King does theme'd stories... I'm not saying one is better than the other, just very different products that require a lot of different sorts of work to complete.
Edit: Another fun fact, many of King's non-Dark Tower books tie into the same universe, check out: https://en.wikipedia.org/wiki/Multiverse_(Stephen_King)