!. How can they maneuver the way they do?
answer: The ships we see are unmanned space craft merely probes set by another civilisation to study our world.
2. Why don't the contact us?
Answer: when we study other species like apes do we rush down to talk to them? No we don't and neither do they wish to talk to us because we are so much more primitive than them.
3. Why don't they come here and take over?
Answer: Perhaps like us sending probes to mars they aren't able to send organic life through space yet. so they like us send unmanned probes instead.
Put yourself in thier position....When we study other races expecially violent species we stay at a distantance and i believe that is what they are doing as well. It could be that they will reveal themselves some day but when they do i think it will be as rulers not as equals.
what are your thoughts?