From Wikipedia:
From time to time, the term "cargo cult" is invoked as an English language idiom to mean any group of people who imitate the superficial exterior of a process or system without having any understanding of the underlying substance. The error of logic made by the islanders consisted of mistaking a necessary condition (i.e., building airstrips, control towers, etc.) for cargo to come flying in, for a sufficient condition for cargo to come flying in, thereby reversing the causation. On a lower level, they repeated the same error by e.g. mistaking the necessary condition (i.e. build something that looks like a control tower) for building a control tower, for a sufficient condition for building a control tower.