User blog comment:Fusedtwilight/SEASON 8!!!!!!/@comment-5123006-20120523032026/@comment-5123006-20120523131158

The way I see it, Sam goes to one or both of them to get help freeing Dean and Cas but double crosses them, pushing them down their villainous path. That or they decide to activate their masterplan due to the decrease in angel activity that could stop them.