It used to be a secret, and apparently various military R&D happened there--particularly of aircraft, which were also secret.

The surrounding area became a hotbed of UFO sightings, some of which were sightings of actual aircraft.

This fueled conspiracy theories, such as that the wreckage and survivors or bodies from the Roswell incident had been taken there for study or storage.

These conspiracy theories experienced a resurgence in the 90s due to the X-Files, but I am not sure what revived the momentum that led to the pathetic 2010s "raid".