You may have missed my point. The case for O’Neill cities in space has to more than a neat thing to do — it also has to be priced out so as to be a better investment than competing big ideas.
I think saving humanity should make it a top priority, but what do I know?
It would also be militarily a strategic asset. Manufacturing hub. Way station. Out of the gravity well for satellite launch and repair. Low gravity medical facility. New materials font. A refuge if needed. And so much more.