They'd been executing small-scale PSYOPs related to UFOs for years.
The first documented appearance of these figures, whom Pilkington calls Mirage Men, and wrote a now infamous book about, dates back five years before the now infamous UFO flyovers at the White House.
Years later, Arnold told reporters that the eventual information stalemate from the military after the crash startled him more than the actual UFOs he'd seen over Mount Rainier.