And if more proof was needed, there's something out there called Shaver's hollow earth one may wish to chase up.
Actually, Richard Shaver believed that his good Teros and bad Deros lived in caverns underneath the Earth's surface. He claimed that he had spent a lot of time in the caverns with the Deros, but it later turned up that he was in a mental hospital the whole time. He had been hospitalized for paranoid schizophrenia, and his Deros were thus likely a result of his mental illness.
Ray Palmer had published Dero stories in his science-fiction magazine
Amazing Stories, stories that he claimed were either nonfiction or fictionalized real events. It got his magazine a LOT of readers, despite the howls of more mature SF fans. His publisher eventually shut down those stories. In 1947, RP founded a magazine named
Fate dedicated to paranormal stuff, and an early issue of it featured Kenneth Arnold's sighting of saucerlike objects near Mt. Rainier from his private plane. This became "flying saucers", and soon, large numbers of people were noticing things in the air that they would normally have ignored. This produced a wave of saucer sightings.
This issue would have died down except for Ray Palmer's championing the extraterrestrial-spacecraft hypothesis. Interestingly, the artists for
Amazing Stories often depicted disk-shaped flying vehicles, thus widely spreading the flying-saucer meme.
Also helping was how Captain Thomas Mantell seemingly got shot down by a flying saucer. That made this aerial dishware seem potentially dangerous.
The US Air Force got into flying saucers out of concern that some of them could be secret Russian airplanes and the like. However, its earlier investigations were not handled very well, and some early investigators apparently came to believe that flying saucers were ET spacecraft. This was despite official rejection of that hypothesis. This led to the likes of Major Donald Keyhoe claiming that the USAF was covering up what it knows about the saucers.