When You start as a libertarian, there are two very broad categories, There's the crypto fascists and there's idealists. The crypto fascists are people whose politics are driven by white and/or male identity politics and they understand from the get-go that that a great way to be racist and sexist but not to publicly acknowledge it is is to promote a politics centered on what white and/or male people have the most of, private property. To the unsuspecting eye, one's bigotry is converted into reasonable, universality, liberal principles about all of humanity abiding by a shared set of rules. They are the "embarrassed conservatives."
The idealists can be broken down into two groups. Those who are pragmatic and who want to advance markets within the context of a mixed economy, think someone like
Greg Mankiw and to an extent the newer Chicago School that emphasizes behavioral economics and some institutional economics alongside the more traditional market centric approach, it's the school of thought that gave us Cass and Sunstein's advocacy of
nudging rather than compulsion. This group are what I'll call "libertarians at the margin.”
Then there's those who ask us to ignore the 150 years of how capitalism has played out in the real world, I'll call them the "Gold Heads." They see fiat currency, central banking, governmental regulatory bodies, and the welfare state as perversions and corruptions of real capitalism and not as the inevitable patches that capitalism needed as it transitions into being the dominant ideology of vast industrialized empires.
There's degrees of mixing between the three groups but broadly, you can divide libertarianism into those three groups.
Those groups will begin to warp and change as soon as they leave the hot house of academia.
The embarrassed conservatives fetishize private property for a reason and when they see the real world results of living in government that frequently prioritizes private property and its returns over people. As long the regime of propertarianism is mostly punishing people whom the embarrassed conservative see as beneath them, they will stay propertarians (the shift from Tea party to MAGA among this group largely happened because private property absolutism was seen as harming white men too much).
Among the idealists, they see the consequences of private property absolutism failing their pro human ideology. What to do? Well, you can decide that human rights and freedom are the ultimate goal, you saw private property absolutism as, on balance, being in conflict with that goal so you reorient your politics. The other path is to stay a private property absolutist and blame capitalism' failings on government intervention. Taken to its most extreme, you're willing to side the
state and it's monopoly of force to bring about your vision of a pure capitalist society.
I cannot speculate about Milei's libertarian beginnings but I know what path he's going down and it involves violence and repression in service of upholding private property absolutism at all costs.