We don't have the trademark, unfortunately, but we can demonstrate using the mark for months before Google did.
I haven't looked, but I am fairly certain that Google has trademarked "Stadia" for the gaming space. You could try trademarking "Stadia" for the mapping space, but that wouldn't prevent Google from using "Stadia" in gaming.
If you have several hundred dollars you're willing to place on a long shot bet, you could talk to a trademark lawyer.