That's true, I just mean it's crazy given how large his books are and how much he has to build up for each one.
That's true. I mean it took Stephen King around five years to write IT, which is like a 1000 page book. I'm not all too familiar with Brandon Sanderson, but I do know that with authors within his domain that there tends to be a lot of research and world construction prior to writing, especially with innovative systems of magic and societal construction if the story is based within a fictional world; thus, it would go beyond outlining a novel and writing it.
I don't know how pedantic his style is (Brandon Sanderson) , but personally when writing fiction within the scope of fantasy it tends to be long and tedious at times. I'll give a bit of context here: Over the course of the last several years I have spent countless hours on world construction and magical systems. I easily spent a couple of hours examining the schism that created the merfolk colonies--not because it has a big focus within my novel, but rather because of the impact it had on the world and how my protagonist grew up, thinks, and acts. So, I imagine even though writing is his career that he spends countless hours on research, writing, and development... and he tends to write, as you said, very long books. I, myself, will write a scene that takes 30 minutes to an hour and I feel like I wrote a lot only to discover it was around 800-1250 words... lol. When Brandon published a book in 2017 that was around 1200 pages and 450,000 words... That's real dedication. So, I admire him for that.