The survival of GrapheneOS is far from guaranteed for multiple reasons, but sure, it's nice while it lasts and stays updated with patches. I think Graphene might benefit from having additional hardware interoperability, and additional security layers that defend it even in the face of delayed patches from upstream.

Sure, but the survival of any Mobile Linux doesn't have better odds.

The way I see it, the more support GrapheneOS gets, the higher the likelihood it survives. The goal is to reach a point where Android manufacturers consider that they lose money if they don't reach the requirements of GrapheneOS, because enough people care about them.