I believe Johns had a story he wanted to tell that would redirect all of DC comics, Didio et al didn't want Geoff to reclaim golden boy status because he would be less easier to control than say a Scott Snyder who would just be the latest top writer as opposed to the Return of a King, with a second reign on the Iron Throne. I believe Doomsday has finished strips and artwork that told a completely different story that had to be rewritten and redrawn mid series because of politics. Just like Bendis Legion was delayed because art had to be redone for the Bennetoning of the cast. I am sure Johns would be po'd if DC begged him to use his "Rebirth" move on all of DC just to pull the plug midstream. Johns has been late but never as late as DC and JSA and strange things were afoot at DC comics coinciding with those badly delayed books.