During WW2 a bomb factory was built near Point Pleasant, WV. It fell into disuse after the war but was not decommissioned.
In the early 1960s it was brought into use again, to test gadgets intended for military use. Three of these gadgets were an exoskeleton (intended to extend a soldier's endurance and increase his running speed,) infrared goggles, and jet packs combined with parasails. There's evidence that they were testing wireless microphones and other gadgets as well.
There were two descriptions of the Mothmen - one or more men on foot wearing brown clothing with goggles, and the traditional silver single flyer.
The "browns" were testing the exoskeletons. They weren't wearing camo brown, more like the brown work pants and brown flannel shirts somewhat typical of what the locals wore. The clothes were very baggy to cover the exoskeletons. The silver flyer's jumpsuit was made of a stretchy silvery weave similar to what you see on oven mitts. His kite had a frame that extended to a sort of foot brace so his legs didn't dangle when he was airborne. He also had the goggles.
I know this because I happened to be in the area at the time, I was with my parents on a business trip. I saw them. So did most of the locals. It's hard to miss some fat guy running at 35 miles per hour and a silver guy flying over the neighborhood.
Appalachians tend to be pretty superstitious. Whenever local kids tried sneaking into the old factory, or when the adults started asking around and talking too much the Men In Black would drop by and be vaguely threatening. When that failed the Browns would come by after dark and scare the residents. Superstition suggested that they were some sort of evil spirits and that the silver flyer was a vengeful angel.
The legend of Chief Cornstalk comes from this period. There was a Chief Cornstalk, he did live there and he did not die peacefully in his sleep. However, he was not lynched, as the legend suggests, therefore he did not put a curse on the area, and there were no brown and silver demons avenging him.
With the infrared goggles the Mothmen could easily see the unusual heat signature coming from the failing eyebolt on the Silver Bridge. Why their superior officers didn't come clean, say there were top secret experiments going on, and as a side effect of those experiments it was discovered that the bridge would - not might - fail is unknown. The wireless mic phone call comes from the lack of action. Someone was concerned and moral enough to try to warn the town.
The rest is history.
