When serving static files, even something like old school apache can serve a couple thousand requests/second on relatively anemic hardware. That's billions of requests/year. The average podcast doesn't really need this.

Even at google's scale, if all their content was static, they wouldn't need that many servers. The hard parts of scale is keeping everything in sync in a distributed system designed to make sure your content is fast everywhere and managing the sheer amount of compute for the dynamic side of things.