Energy (Score 1)

Drej destroy Earth because of the titan. Why? I say because they saw that it would take alot of energy to do it. And although they developed a power plant to do it with, it could still be used as a weapon against the drej. The Drej were the bigdaddies on the block. When the humans developed a weapon that could potentially destroy them they blew up earth. The destruction of your own race is about the only thing that would motivate me into destroying anothers. just my 2 cents