Maybe they just want to make a new Castlevania WIHOUT Iga at the helm. Maybe they want to try a new direction with it and give someone else a chance to envision Castlevania, but they also realize that Iga won't give up the reins. If they take a chance and force out Iga, they would lose him permanently, and if the game doesn't pan out then Konami is left stranded.
Just a thought