It’s Google Maps, not Alphabet Maps. Isn’t that a similar situation?
And it doesn’t dilute the Google brand, if anything I’d argue it strengthens it and makes it even more well known.
Mozilla created Firefox.
It’s like if Google decided to rebrand Google Maps to Chrome Maps if Chrome ended up having better brand recognition.
It definitely hasn’t gotten to a point where we’re getting Chrome Maps, but the proliferation of Chrome-branded devices does indicate that Mozilla focusing more on Firefox the brand is a reasonable decision.
At one point it basically did, since Chrome was (IIRC) the first thing to support casting to Chromecasts.