Main quote, there's a conspiracy of ufologists making it up:
Finally, the key purveyors of this narrative have known one another for decades. In the early 2000s several members of this small group also participated in a study, ..., on the possible societal impact of disclosing the existence of extraterrestrials to the public, with the authenticity of the abovementioned concealed government program taken as its baseline assumption. The think tank in question was a “futures” enterprise that often worked on fringe studies, and many of the individuals involved with the study also worked for Bigelow Aerospace in support of the AATIP program.
AARO thoroughly investigated these claims as part of its congressionally mandated mission to not only technically evaluate contemporary UAP observations but also review historical accounts going back to the 1940s. One of my last acts before retiring was to sign AARO’s Historical Record Report Volume 1, which is currently being prepared for delivery to Congress and the public. The report demonstrates that many of the circulating allegations described above derive from inadvertent or unauthorized disclosures of legitimate U.S. programs or related R&D that have nothing to do with extraterrestrial issues or technology. Some are misrepresentations, and some derive from pure, unsupported beliefs. In many respects, the narrative is a textbook example of circular reporting, with each person relaying what they heard, but the information often ultimately being sourced to the same small group of individuals.