GeckoEidechse

Not only was it not very successful, it’s an old outdated Microsoft playbook from the 90s/early 00s and was targeted at closed source competitors and freeware, not open source software where you can just fork out a separate version.

In Microsoft's case I agree. However Google successfully used EEE to essentially kill of XMPP where they initially added XMPP support to Google Talk, then extended it with their own features which weren't up to spec, and then later killed off XMPP support.

Yes XMPP still exists but I'd argue compared to previously standard XMPP is no longer as widely spread. Where as previously you would have people talking to each other over different XMPP services, that kind of federation no longer exists. For example WhatsApp supports XMPP but good luck trying to talk to WhatsApp from another client.