there was the possibility that they were, in fact, “cutting-edge secret weapons or spying drones in disguise” that could “pose a significant threat to our nation’s security,”
This is key - back in the early days of UFOs, a number of those that didn't have more mundane explanations were top secret American aircraft, so the military took an interest in the field if only to add misdirection. These days, any number if hostile actors could be sending up advanced drones or aircraft and you need to ensure your airspace is secure. It would be unwise to dismiss everything as flying saucers.