My friend,,,, somehow I knew that would be your reply.
Your premise it that EJ was DM's guy and not DW's guy, Here are two important links to read, The first supports the development plan of EJ as THE original plan and the second supports the Lame Duckness of Douggie as well as the continued plan for EJ.
Please read this carefully as it bears a lot of weight.
http://www.foxsports.com/nfl/story/ej-manuel-buffalo-bills-benched-kyle-orton-doug-marrone-doug-whaley-092914
they drafted Manuel to develop behind Kevin Kolb, who was acquired that offseason. Kolb, though, was placed on the injured reserve before the regular season ever began after sustaining a concussion. While Manuel was rehabbing a minor knee procedure during the preseason, undrafted rookie Jeff Tuel was penciled in to begin the season under center. Manuel, though, would return in time. In 10 games last year, Manuel showed flashes of brilliance, but was far too inconsistent, throwing 11 touchdowns and turning the ball over 12 times.
http://www.syracuse.com/buffalo-bills/index.ssf/2014/12/doug_marrone_has_no_plans_to_replace_kyle_orton_with_ej_manuel_regardless_of_bil.html
Even as the team stares down the barrel of elimination in the final weeks of the season with Orton struggling, Marrone says the Bills will stick with Orton because he gives the team the best chance to win. Even if the team is eliminated from playoff contention, Marrone says that stance won't change.
>> WHY wouldn't he want to change? Did he care if the Bills made the playoffs?
Back when Marrone benched Manuel for Orton, he made it clear that he was not looking for agreement from general manager Doug Whaley or the front office on the decision.