From what I can see, podcasts vs Clubhouse is a bit like Youtube (without streaming) vs Twitch. One is more spontaneous and interactive whereas the other is consuming content.

I'm guessing it's the sense that users get to participate as well (probably more than a normal stream or Twitch stream) which interests people, the value proposition is being able to contribute to a Joe Rogan podcast as a roundtable discussion instead of just listening to it.