I was thinking this very thing as I watched. When they put someone in as host who *ought* to be good, the show's a stinker. When they put someone in who's more WTF-are-they-thinking (Elon Musk, et. al.), the writers come up with good material. Maybe they work harder.
Edited to add another possibility: When they put in a person with sketch experience who really doesn't understand the show, that person says, "Hey, I know what would be good!," and it isn't. When they put in a person who absolutely doesn't know what they're doing and knows it, the writers have free reign to create.