The idea is that in the near future,man is quickly advancing. The rise of superhumans have led to the ability to synthesise new materials,making everything smaller,lighter,and stronger. Aliens who have recently discovered Earth are deeply afraid. They realize that the Human race advances so quickly that in 50 years we'll be so advanced we'll be more than powerful enough to overpower nearly any other force in the galaxy.
Solution? Wipe them out before these Humans become a threat.
I really wanted to theme this story off of the trope Humans Are Special
Also,I really need some advice on how to tell Earth's backstory since this takes place 70 years in the future,and things have rapidly changed. I'm not entirely sure how to explain the backstory in a detailed way that would be enough to keep the audience from being confused about how all these changes happened. I don't want to leave a bunch of plot holes about the past.