So Joshua Hale Fialkov left Green Lantern books because DC wanted kill "John Stewart" to cut down on Earth Lanterns.
Edit - "I understand that both the editorial input for both Fialkov’s books, and fellow walker-outer Andy Diggle‘s Action Comics, were in direct contradiction of the promises made at the DC Creative Summit by Dan DiDio, backed by Diane Nelson, that once an overview of an arc had been greenlit by editorial, it wouldn’t be changed by editorial. One creator told me that the promised lasted four days."
Four days!!