Everything except nothingness, that is, everything, has the Ground-Grounded structure.
The error of the atheist is to think he can remove the Ground of Grounds, God, and yet still have everything which is Grounded in God—which strictly, is everything—but more proximally is the Good.
Atheism entails nihilism because God qua the Good is the ground of morality/ethics. Remove the Ground, remove the thing. Nietzsche knew this.
In any line of reasoning that goes wrong, there will be a POINT it goes wrong. This is the πρῶτον ψεῦδος.