Additionally podcast revenue is heavily centralized, which warps the kind of programming around the whims of the sponsors - who are often Amazon or a subsidiary company of another Fortune 500.

Within a margin of error I'd imagine virtually all tech centric web content has at some point been sponsored by Audible (Amazon), Squarespace (private), Dollar Shave Club (Unilever), or rarely one of a few VPNs like Tunnelbear or Private Internet Access.

Isn't the idea of decentralization for podcasts to create an open protocol that anyone can conform to at their choosing? It is the choice of the content creator in those circumstances whether or not they join together in a group. Just because clusters form in a decentralized system doesn't mean the entire system isn't decentralized.

Organisms do find it easier to survive in groups, but the main point here is that even these groups like Nerdist, NPR, etc. would still have publicly available working podcast feeds if somehow iTunes stopped working tomorrow.