User blog comment:The Milkman/Everybody Shut Up./@comment-4553238-20120424234358/@comment-1221773-20120425000802

Vendetta states that the Citadel was moved to Earth so the Reapers can better defend it. By game's end, Earth is at the heart of Reaper-controlled space and presumably has one of the largest contingents of Reaper ships nearby.