Warner bros is being divided into the cable TV stations + discover channel stations and the movie studio and the backlog is separate.
Netflix wants the movie studio + tv back catalog
The Hobbit for instance is a WB production, not Newline.
Apparently sometime shortly before they got the axe they paid Susanna Clarke a 7 figure sum to option Jonathan Strange and Mr Norrell. I don't know a whole lot about options but 7 figures sounds like about 8-16x what people usually do especially for a 3 year old book by an unknown author. IIRC, that's more than Andy Weir got for The Martian. And more than Lev Grossman is worth today, and he got five seasons out of three books.
That option expired unused and BBC One and Cuba Pictures made it into a very good miniseries. Does feel a bit like a pattern of financial exuberence.
Also Clarke has a chronic illness, which is preventing her from trying for another book of that caliber. That mountain of cash is probably keeping her very comfortable.