Wim T. Schippers is a well-known funnyman who has done many crazy things in the great Dada/Fluxus tradition. For instance, 'Going to the Dogs' was the title of his theatre play for six dogs -another hilarious classic. Things are always going awry in his shows - they should, in fact. And as a sideline, he does Ernie's voice in the Dutch Sesame Street show. (which he does well)
The Nazis made the connection with mental illness to wilfully discredit modern artists. The thought is surely fascinating, but let's not fall into the pitfall of assuming something similar for our scribbling ancestors. Just because something looks crazy, the person who made it does not have to be crazy.