I don't get the XMPP thing. XMPP was an obscure protocol mostly used in non-federated applications (several MMOs use XMPP for in-game chat for example, obviously not federated). When Google and Facebook adopted XMPP and federated, the user base exploded, sure. Then they defederated, and XMPP went straight back to where it was before. There was no EEE - it was EA: Embrace, Abandon. Google and Facebook didn't extend or extinguish anything. If anything, Slack and Discord killed XMPP, not Google.
Perry