The subject line doesn't seem to match with the the post it links to - perhaps it's been updated since being shared here? The blog post right now is titled 'the ecosystem is moving', and in the first paragraph states:
"Nothing about any of the protocols we’ve developed requires centralization; it’s entirely possible to build a federated Signal Protocol-based messenger, but I no longer believe that it is possible to build a competitive federated messenger at all."
...which is is a far cry from "why federated protocols don't work". A more accurate headline summary might be "why we believe federated protocols are not competitive for this use case", which has a different ring to it.
"Nothing about any of the protocols we’ve developed requires centralization; it’s entirely possible to build a federated Signal Protocol-based messenger, but I no longer believe that it is possible to build a competitive federated messenger at all."
...which is is a far cry from "why federated protocols don't work". A more accurate headline summary might be "why we believe federated protocols are not competitive for this use case", which has a different ring to it.