> don't remember anyone else who's resulting laughs seemed so inadvertent or by chance, like he was ill-prepared or crazy, or both
None of it was by accident: He was really good at comedy and was getting exactly the laughs when/where he expected them. Coming off as ill-prepared was a shtick.
Bill Burr and Bert Kreischer have a podcast. Once, Norm came up[1]. What they said is something I've heard from pretty much any interview about him: Norm is the quintessential comedian's comedian. He's up there trying to do what he thinks is funny, audience be damned.
None of it was by accident: He was really good at comedy and was getting exactly the laughs when/where he expected them. Coming off as ill-prepared was a shtick.