> [...]if Libertarian societies were superior then they would naturally outcompete other societies[...]

Not for the lack of trying. There have been more than a handful of Libertarian city takeovers and sea-steading projects, and they all end in similar, predictable ways. The sea-steader/new country declarations fail to defend "their" territory against an actual military, and the libertarian towns run out of money and/or people willing to live in a free-for-all society without common services.