All you mention are possibilities. And I think it is something along those lines in general. I like a good mystery and learning the eventual outcome.
“All you mention are possibilities”
I like a good mystery too! Extrapolating based on pretty thin evidence.
There are drone arrays flying over uninhabited areas of the west. Maybe something I write will click in someones mind and they will remember something that can add to the total picture!
Another...maybe its goverment census of nocturnal animals in the western plains. Maybe of Daytime animals.
It could be the military testing military use drone arrays for use as a battlefield survellience device. Not unusual for western states.
Honestly, military testing and natuaral resources, including meteorites, seem most likely to me.