No Campaign Co-Op In MW2, Infinity Ward Explains Why
Developer Infinity Ward has revealed a campaign-based co-op mode for Modern Warfare 2 was originally planned, but was later dropped once discovering that it “ruined the experience” after extensive playtesting. That scrapped mode was later reborn as Spec Ops, a mission based co-op component comprised of levels that IW felt were more tailored towards cooperative rather than solo play.