Gtalk did not kill XMPP. Very few people were using XMPP before Gtalk, most people were using AIM, ICQ, MSN, Yahoo Messenger and other proprietary protocols. Gtalk supported XMPP to gain traction as a more open messenger and possibly because they implemented the original version on top of XMPP to get it out the door faster.

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.

Jabber was big with the "federated, decentralized" crowd. I recall several colleagues who established Jabber addresses and advertised them, sometimes as their only IM address.

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.