In this case, it's because aliens have
misread a video feed of classic arcade games
as an act of
aggression, and send their own versions of Donkey Kong, Pac - Man, and others to destroy the puny Earthlings.
There are always reasons for behavior, and when
aggression becomes a problem the reasons can be such things
as improper handling, lack of socialization or training, a
misreading of dog behavior by the owner, or, rarely, disease.