The whole ATC system is based on the underlying idea that stuff isn’t supposed to be in certain places at a certain time. For example the system can operate without radar in zero visibility conditions because it can use a “one in one out” philosophy where a certain 3D block of the Sky only has one flying object in it. Random drones, jet packs or whatever turning up unannounced in busy airspace totally destroys that system (irrespective of other issues) hence why when something like this happens you see the FBI rocking up and treating this like they are.