She 'played/acted dumb' [=pretended to know or understand less than she really did] so we would assign her the easier tasks.
She thinks television is contributing to the 'dumbing down' of America.
Cutting training programs will 'dumb down' the American workforce.
(..) I figured, after we married, I'd have to stage a little accident for Elsa. Hans. No, stop. But then she doomed herself, and you were ...dumb enough to go after her. Please. All that's left now is to kill Elsa and bring back summer. You're no match for Elsa. No, you're no match for Elsa. (..)2013 Frozen