There is an old documentary called "The Sad Clowns" and it's about the great comedians of the early 20th century (Chaplain, etc) many of whom based their routines around "pathos". Comedy often is an attempt to transcend personal pain. Certainly people find me the most hilarious when I'm talking about my insecurities or heartaches. It's a weird thing, but true -- the content do not know irony.
So true, Robin Williams was a blatant example of just that.................