Dangerfield's shtick was being as shitty as possible in every possible way. He pretended to be a terrible human being, a terrible comedian, a terrible everything. It was hilarious.

A lot of people weren't in on it though. They thought he was washed up, not knowing that that was the joke.

Another good comparison would be heels in professional wrestling. Those people work hard to get as low as they are, and they suffer for it as much as the medium benefits from it.