I think, many of you after watching Covenat considered that David just killed all Engineers. But what if there's actually no his guilty? So, here are my thoughts. In the end of Prometheus Last Engineer tries to launch Juggernaut and wipe all life on Earth. And then David reveals that there're many ships on LV-223. What if there is some kind of net between all these ships and Last Engineer's comands spread on all of them? What if ship that Shaw and David used to travel to Planet 4 was already set to drop its cargo when arrived to destination?
Yeah, i know there's many possibilities to argue that statement but what if? I prefer to think that David's insanity is result of his 10-year isolation without any control over him rather than he was already insane and straight evil when arrived at the planet. You know, he just had way too much time to think about morality and value of human's life and there was already a lot of dead bodies and pathogen to experiment on and there was not too many ways to keep himself busy.
So, what if?