... Well. My official explanation in my head was that, because Kurt had inspired Earth to take over the world with him, that had made Earth a large enough threat to be eliminated. That's why, because they idolized Kurt, they made themselves a large enough presence that the Ruwdans felt the need to blast them all to pieces, and that's how Kurt was responsible for humanity destroying themselves through being inspired to fight by him...

But eh. Suppose that didn't do it. Hah.

I'll make a more proper reaction to the reviews a little later.