I think there's two options for UFO sightings:

A) there are real, ET or machine intelligence piloted UFOs actually visiting us - or -

B) this whole thing has been a long, slow burn disinformation campaign to reduce the risk of nuclear war by scaring nuclear weapon powers into believing there is something with greater power out there capable of quickly eradicating nations that move to aggressively use nuclear weapons

I'm leaning towards B, personally. Just makes more sense to me - make people afraid, unsure of what's out there - give leaders just enough doubt to second guess pressing the nuclear button.