IPFS hosting is provided by volunteers running IPFS nodes.
To provide maximum benefit for podcasters while balancing the storage & bandwidth resources of volunteer IPFS nodes, episodes are hosted for a limited time based on their popularity.
The deafult hosting remains on IPFS until there have been no plays/downloads for 48 hours. If a show is popular, it will remain on IPFS. If no one is listening, it will be removed from the volunteer nodes.
Anyone can run an IPFS node and volunteer hosting resources. Nodes have the option to "Favorite" podcast feeds to signal their support by hosting entire feeds on IPFS forever (until they un-favorite). As more nodes favorite a feed, decentralization grows, resulting in faster downloads and better performance.