Just like any other kind of media the only money is when you have high production value with a machine behind you and/or you have talent and can stand out.
Podcasting became incredibly saturated in a very short matter of time. Everyday you see a clip of a new podcast talking about the same old tired and overused points.
Also there are too many poorly produced podcasts. shytty audio and shytty lighting with nothing to talk about. Being 90 minutes and all over the place with no flow. Nobody in their right mind would throw money at that.