One of her wonderful worldviews was to rejects altruism as a moral imperative, arguing that individuals should live for their own rational self-interest. Social security, based on the idea of supporting others, contradicts this principle.
Which means anyone whose wisdom matches their self-interest is going to understand that different things have very different efficiencies at different scales.
And some things happen to be dramatically more efficient/person and more effective, the larger the scale they can be coordinated at.
This exactly. All of these people who profess to believe in objectivism could easily move to a failed state and do anything they want to with zero government intervention. But they don't do that. They want all of the benefits of a working government with none of the things required to actually create a working government.
This position was already pointed out by Plato (in the Gorgias IIRC) as being inconsistent. Political systems are made up by people - if a society, in particular a democratic one, has certain systems in place, then this is probably because it was (at least believed to be) in the people's self interest.
https://www.openculture.com/2016/12/when-ayn-rand-collected-...