I don't think the issue is that the left wouldn't allow similar content, it's that the left isn't interested in that content. I'm not stupid so why would I be entertained by 3 hour conversations on how aliens built the pyramids, the moon landing was faked, vaccines are bad, Hitler was misunderstood etc. I would compare it to how some people are fascinated by streaming slop - bad television shows and films that are designed to appeal to people who are browsing their phone while watching "content." I like watching good films and tv shows so why would I waste my time watching bullshyt I know isn't made for me? But as we've seen over the last few years, streaming slop is very popular. More popular than many of the films and shows I enjoy, in fact. It is what it is.
I wouldn't expect liberals to overtake conservatives in podcast anymore than I'd expect conservatives to overtake liberals in Hollywood. These are very different groups who have different interests. Liberals actually listen to a lot of podcasts, they simply listen to different types. Crime/serial killer podcasts, sports, entertainment/gossip, etc. It's just not all linked together by a political ideology.