emphasis added. they could hardly take advantage of UFOs given that the topic remains just barely in the Overton window, if at all. I attribute that to deliberate misinformation but also to the existence of independent hoaxers.
as for the motive to keep them secret, given the timespan involve, never mind my outsider status, hard to say.
but the ostensible reason has had to do with not exposing the public to ontological shock. particularly in terms of the religious consequences, IMO. a more selfish reason has to do with not incurring backlash and for corporations to maintain monopolies on NHI-based technology.
although, I do find it strange that not only the US but other governments have kept quiet. perhaps they actually know pretty much nothing.
at any rate, I think that the documentary The Age of Disclosure goes into it a bit. I have seen the documentary but I don’t remember whether or not it odes. you also might want to go through r/ufos on Reddit where they’ve talked about “why keep it secret?” a number of times.
answering your second question, you’d have to do two things. one, give a natural explanation for why people have vivid waking dreams lasting hours. no, sleep paralysis doe snot account for it. also, I do not mean cases of addictions recovered under hypnosis. because suggestibility, duh.
seance, you’d have to show me records of the US purposefully fooling the public (with technology that I don’t think exists, at least didn’t it, say the 1970s). although I do think that mundane advanced technology does account for some percentage of the cases.
I can, for sure, imagine that the US government knows far less than claimed and have built up the disclosure movement for its purposes. physical phenomena and the entity encounters… well, that would take a lot of disproving.
not vivid dreams. vivivd waking dreams. I only used “dreams” for convenience. this has to do with semantics, anyway. you know what I meant.