It's funny to think some believe advertising doesn't work on them because they're more of a critical thinker. Reality is that it works on everyone, when done properly, and we have piles of science to back that up.
Time and cost to create an investigative podcast is substantially more than just some idiot sitting around BSing about whatever pops into their mind. But as the listener numbers show, people love that stuff. While the true crime stuff did pull listeners, it's now been beaten to death and most of them don't offer much unique. With only so many ad dollars for those audiences, they spread things too thin.