Doesn't Joe Rogan typically have a bigger audience than an average so-called-mainstream news program? The economics might play out that it is more expensive to get him to endorse something than get it run on a major network.

There aren't many (any, really) quality guarantees on non-podcast media anyway. It isn't like they get any negative feedback when they lie or make mistakes. Viewers can't even withdraw support for specific known liars on a channel. It is unclear why a podcast would be at a structural disadvantage to any other media source, and probably higher reputational stakes.