Why is libertarianism so infallible?

It is due to it being the application of political science. It does not permit failed policies to be continued fruitlessly year after year with idealistic fervour, it is next to impossible for anyone surrounded by fierce libertarian critics to continue clinging on to lies. It is a purely functional machine, lubricated with justice and fueled by free speech.

All freedom, all the time.
Whatsoever therefore is consequent to a time of war, where every man is enemy to every man, the same consequent to the time wherein men live without other security than what their own strength and their own invention shall furnish them withal. In such condition there is no place for industry, because the fruit thereof is uncertain: and consequently no culture of the earth; no navigation, nor use of the commodities that may be imported by sea; no commodious building; no instruments of moving and removing such things as require much force; no knowledge of the face of the earth; no account of time; no arts; no letters; no society; and which is worst of all, continual fear, and danger of violent death; and the life of man, solitary, poor, nasty, brutish, and short.

It must be comforting to know there's nothing to catch you if something goes wrong.