My apologies, I meant to say "This American Life in podcast form", or take Serial as an example that's often quoted.

But it basically stresses my point. It could very well be that it was a direct inspiration for the first podcasts, but nowadays it's used as "audio content, often episodic". Also people often name the production value and other criteria of the big ones. But my point is that podcasts are on average not high production value or even done by companies or in the type of certain radio programs. I'd even say a sizable chunk is just the same people talking about the same or related topic(s) - I don't think I've ever heard that format on a radio station. (Except the same person interviewing different people, if that counts as "the same topic".)