What the IETF (or any organization in a similar position) sought for its discussions was an existing off-the-shelf product, not a protocol. They chose Zulip, b

What the IETF (or any organization in a similar position) sought for its discussions was an existing off-the-shelf product, not a protocol. They chose Zulip, because it is a product that has various features that are attractive for the IETF's use cases. The protocol it uses internally is pretty irrelevant from the IETF's perspective, as a user. If the IETF had developed its own chat tool and did not use XMPP for that, your comment would have more weight.