Yup, it was Dim.
"Good pilot, I'll give him that. But the brains of a child... the Emperor's
plan was too complex. If he had dangled a cupcake in front of Luke and said
"Look! Cupcake! Join the Dark Side and you can have the cupcake!"
Then Luke would have just gone
"Ooh! Cupcake!" and that would have been it."