What were stopping Aliens from attacking with those advanced weaponry?

From wiki

In an alternative 1982, an alien ship has inexplicably stopped over Johannesburg. When investigation teams enter the ship, they discover a population of sick and malnourished extraterrestrials, identified derogatorily as "prawns".

So the reason behind that aliens let them be treated like hostages could be explained with this. They were weak and sick. So they avoided war at beginning. They turned the place into slums and was living there miserably.

But the movie plot starts after 20 years have been passed. So why didn't the Alien attack with their advanced weaponry and free themselves from such cruelty of humans. They were having advanced war suits that Wikus used later. I'm guessing that war suit needed to be initialized by the remote ship that later took Christopher Johnson(Alien) to the mother ship. But they had more advanced guns, bombs. Why became slaves for over 20 years when they could try to fight back.

Am I missing something here? Is there any reason for which they were not attacking?

plot-explanation district-9

Best Answer

Director Neil Blomkamp has revealed that the "prawns" are a hive-like species, much like bees, who have somehow lost their queen. All of the prawns we see are "drones" who can barely think for themselves, and they definitely can't organize themselves towards a common goal. Since they were never given an order to fight back, they were contented with living in slavery. Christopher Johnson seemed to be the exception. He worked diligently for twenty years to gather enough substance to fuel his ship. While Blomkamp didn't specify either way, fans speculate that Christopher was a different class of prawn with higher mental facilities, perhaps even a soldier.