They picked a villain with an expressive, manic face and decided to make him into a rigid plastic mask. They then went and cast an actor with the perfect expression range (as well as generally looking fuckin creepy most of the time) to match and covered him with said rigid mask. It was a ginormous waste. His voice is perfect, his face is fantastic when he's ranting at his mirror. All they had to do was paint the guy green and it'd work.
It'd be like casting the joker and making the actor wear a plastic hallowen clown mask.