Because of the way they move. Just read lots of older witness reports and you'll see that they move in a more radical and sudden behaviour. They move
too "soft", much like "Star Wars/Trek"-spaceships.
In the short clip that is seen over the fields all four objects can be seen quite clearly, there would have been little time to react, and the
camera has just about captured all four.There is no zoom in, the later closeups are post filming.The film then has been edited, but there is no info
on who did it,Von Raven or the actual cameraman.