Except XMPP uses DNS for message routing from a human readable handle, [email protected], but Matrix uses a central database "identity server" operated by Matrix.org and federation fails if this service goes down.
So Matrix is like XMPP, except that XMPP is really federated, but Matrix's "federation" is partial and therefore it's mostly marketing.
Matrix is really mostly marketing overall. That's part of why it's so popular here; HNers love shiny bullshit. Honestly XMPP is a better protocol, it's even still being updated and has many more server and client implementations, including modern ones, but Matrix has great PR.
So Matrix is like XMPP, except that XMPP is really federated, but Matrix's "federation" is partial and therefore it's mostly marketing.
Matrix is really mostly marketing overall. That's part of why it's so popular here; HNers love shiny bullshit. Honestly XMPP is a better protocol, it's even still being updated and has many more server and client implementations, including modern ones, but Matrix has great PR.