or . . . as some put it . . . to enslave, robotize, coerce the masses to comply overwhelmingly and precisely as needed amidst varying levels of chaos, terror etc.
But why would an advanced civilization need slaves?
With our present technology we barely need workers today. With in a few decades nearly every unpleasant task that a alien race would want to do on our planet (mining I would guess) could be done cheaper and more efficiently by robotic mining equipment.
Unless enslaving other races is their hobby I can’t see a purpose in conquering the earths people.
I they wish to inhabit Earth it would make more sense to be to exterminate the human race.
To me the most realistic Sci Fi movie on this vein was Independence Day.
When the President ask the captured alien what they (the aliens) want from the Earth’s people the alien replies “We want you to die.”
If the aliens arrive on Earth and they do not announce themselves as I see it they have only two possible motives;
The first is benign and that is to do anthropological studies.
The second is malignant and that is to study us to discover the most efficient method of eliminating us.
For an advanced civilization the second would not take long and eliminating us would not take much longer. For the first it could almost all be done form outside of the atmosphere by listening to our electronic emissions.