Screens, bubble screens, play action pass, draws (aka constraint plays) are all used when a defense is cheating. They are not always used for the mere sake of being a single successful play but rather to keep a defense honest throughout the game. When the Redskins, or any team for that matter, cheats inside to stack the run game bubble screens are an effective way to make them back off and respect the boundaries. It's really that simple and there's nothing more to it.