[throwaway60607]

Why trolls? Maybe they just want to learn about us. I don't see the reason to assume they have godlike sensors with unlimited range - they need to come closer to see detail.

Them being able to travel here doesn't imply they have significantly better technology than we do - it just means they had more time, perhaps their civilization is older than ours. 100k years older would be enough to send out a probe from some nearby stars. 1M years older would be enough to travel from thousands of not-so-nearby stars around.