Originally Posted by DarthSkywalker
They weren't going to harvest. They went looking for the codex. They also never intended to harvest Earth, they wanted to raze it. Got to keep up.
Semantics. They wanted Earth for their own. The story was written so that their other bases were now inhabitable. Earth became the only place. CONVENIENT. Isn't it also convenient that the Codex ended up on the only place they could build a new world on.