The cryptozoological nature of the phenomenon makes me think that in
Nope's universe, not only UFOs, but also ancient Legends (like biblical stories for example) may be interactions between humans and this animal, totally unknown to science. Although the fact that they don't explain exactly what it is gives it a touch of cosmic horror.
Oh and listening to people and horses being digested by Jean Jacket was very creepy, not to mention that scene when Otis pokes his head through the door of his truck to look up and see that thing and then say
'Nope!' It was both scary and kinda funny.
I also read that the pandemic and its consequences inspired Jordan Peele to create this story...