Enoch and the Nephilium
The Nephilim that Enoch spoke of are the children of the fallen angel's seed (the demons), that lived on the first earth, and the earth now. Enoch gives a precise description of them.
If the fallen angels came to the first earth, what makes you think they haven't harvested this earth? They did. My proof is the bible, which gives the knowledge of the sins that inhabit the earth before, and now.
The world before had more immoral sins that came from the fallen angels. You can read what they were. Now, note the immorality of today and how similar things appear to be.