Difficult to explain, and the writer shows some fear that seems appropriate for the time period. The writer doesn't speculate as to what they saw out of fear of reprisal from God, and otherwise seems terrified in general. Also written accounts are rare.
I think we should remember, however, that humanity can be pretty creative from our own perspective. Look at Hollywood for the things we're capable of dreaming up, and then bear in mind that humanity has had that creative spark for its entire lifespan. There's a surprisingly good chance that the whole aliens thing is a phantom in the human gestalt, something that enough of us have wished to be real and enough others have hoaxed into life that it now has a life of its own.