

It was intended as an ICQ replacement, and its advocates even managed to sell it as that for many normies. It became supported, with federation or not, by many email service providers, social networks, and so on. Then that support mostly vanished. Its users percentages are not inspiring.
Getting rid of monoculture via transports and cryptography being pluggable (meaning that the resulting system would be fit for sneakernet as well as for some kind of federated relays as well as something Kademlia-based, the point is that the common standard would describe the data structure, not transports and verification and protection).