When a smaller network tries to be interoperable with a larger network, the larger network almost always eats up the smaller one. This is how XMPP was killed by Gtalk, if any of you are old enough to remember.
Gtalk did pull the plug on XMPP but that didn't really change much.
I don't remember EVER interacting with someone with their own XMPP server. Gtalk had nothing to kill.
XMPP was more than Gtalk, but I think that Gtalk was the "death knell" for XMPP, having absorbed it and sort of claimed it as their own. Anyone who would've used federated Jabber addresses in those days is using Mastodon now.
Yeah, just like today, all 4 of them.
Gtalk put XMPP briefly in the spotlight, but for the masses, XMPP never really lived. It was a niche protocol with very niche usage. Just like Mastodon today.