They focused on delivering a secure user-controlled operating system for phones. They used as a base an OS stewarded by an advertising and spyware company which couldn’t have values more directly opposed to theirs. They focused primarily on hardware by that same company. Other hardware was not supported in what sounds like “perfect being the enemy of good”. Eg: other devices might have been less suitable if you were targeted by a nation-state, but would have been superb for the 99%, and also avoided funding their opposition.
They let their antithesis have all the cards. It’s been an uphill battle which they’ve managed to push hard. But it’s hard to see a future, just as it’s always been hard to see a long term future for GrapheneOS.