Torrents won because of search. Each torrent site maintained an index of torrents and you could search that index. Nobody could pollute the index with nonsense entries because the index was curated by the site admins.
There was no good way to search ed2k or gnutella or the other P2P systems. There were many independent indexes (hosted by nodes) like Torrents, but they were not curated by any trusted custodian. Anybody could publish an index, and your client would fetch all nearby indexes and search through it. These indexes, because they were not curated by trusted custodians, and because there was no cost to publishing a list with a bunch of nonsense in it, lead to a terrible spam-filled search experience.
Federation is great when you have multiple repositories of information and users choose which repository they prefer. That’s what Torrent search sites did. If you need a single repository that is in sync for all users and is curated in a P2P manner and you can’t trust all participants of that system to be “good actors”, that is where you need a system like blockchain, there is no other decentralized way to solve that problem.
I wrote a lengthier post about federation vs blockchain as data storage and reputation mechanisms if you are interested lemmy.ml/comment/8051480