I’m looking into hosting one of these for the first time. From my limited research, XMPP seems to win in every way, which makes me think I must be missing something. Matrix is almost always mentioned as the de-facto standard, but I rarely saw arguments why it is better than XMPP?
Xmpp seems way easier to host, requiring less resources, has many more options for clients, and is simpler and thus easier to manage and reason about when something goes wrong.
So what’s the deal?
WhatsApp is using a complete fork of the XMPP specifications and never had influence on XMPP. In the early days when Facebook messenger was using XMPP as a C2S interface they had a bit of influence but what you said used to be much more true for Google some years ago and what happened there is a major reason why people don’t want Facebook to become influential in ActivityPub (which it isn’t yet).