Matrix works well as a big distributed graph protocol, not so much for chat. XMPP works well for chat or anything where you need efficient near-realtime streams (eg. stock trading and tickers sometimes use XMPP, some accessibility caption systems, etc.). Also XMPP is better standardized (by virtue of having a long-term non-profit standards body, Matrix is sort of trying to do that, but also trying to figure out how to monetize it which is never a good recipe for long term success when your spec becomes part of your product).
However, the protocol itself is governed by the Matrix.org Foundation acting as a neutral guardian (https://matrix.org/foundation/), so it unclear how the spec itself would become part of the product.
To suggest that Matrix itself is not well suited to chat is to ignore the rapid adoption of the protocol now used by millions of people.
It really doesn't have massive adoption; it looks big because we're in a little bubble of people who play with new tech on HN, I suspect, but overall other protocols like XMPP are used by a vast number more companies and daily users.
The matrix foundation has had trouble trying to fundraise to pay developers, it's not a proper non-profit standards foundation, in my opinion. I'd be skeptical of trusting them.
I was replying to your previous comment that Matrix as a protocol is not suited to chat by pointing to the millions of people who use the service as a means to refute the point.
The Matrix.org Foundation is a non-profit UK Community Interest Company. As you might expect, it accepts donations which can be used to fund work on the project. It reports publicly on its financial status in the same was as any other UK CIC is obliged to. This doesn't seem very controversial to me.