Mindscape is roughly in the top 20 science podcasts (also #3 in physics) and his books regularly make the NYT bestseller list. So he's definitely popular, but perhaps still underrated relative to the quality of his content. His approach is more idiosyncratic than the most popular science communicators. He focuses mostly on the topics that interest him and isn't averse to getting technical in certain discussions. I think that naturally limits his audience, for better or for worse.