The planet earth is a kind of lab for them. It's like a exploration colony. They lived in Earth in the early ages as emperors, take a look at this post:

https://steemit.com/history/@dralex/the-ramses-ii-skull-mystery

But the governments are hiding the facts from us. I think they rule the Earth in the shadows. They have the best technology and we are the lab's monkeys. We don't even need to know who they are, so we can't revolt against them. It's more smart.