The convergence of conspiracy theories with UFO beliefs is worth examining for two reasons. First, it has brought conspiracism to a large new audience. UFO writers have long been suspicious of the U.S. government, which they believe has suppressed crucial evidence of an alien presence on Earth, but in the early years they did not, by and large, embrace strong political positions. That began to change in the late 1980s and early 1990s, with the first appearance in UFO circles of references to right-wing conspiracism. Over the next decade, such borrowing accelerated and, as a result, brought right-wing conspiracism to people who otherwise would not have been aware of it.
Second, this combination provides a striking example of a new and growing form of millennialism, which I call improvisational millennialism. Unlike earlier forms, which elaborated themes from individual religious or secular traditions, improvisational millennialism is wildly eclectic. Its undisciplined borrowings from unrelated sources allow its proponents to build novel systems of belief.
– A Culture of Conspiracy: Apocalyptic Visions in Contemporary America (2013)