User blog comment:Commdor/Questions for Mass Effect 3/@comment-118213-20101216230959/@comment-2.120.248.98-20110102034615

I had a thought. In ME1 Vigil states that the Reapers attack the Citadel first, and then use the information on the races there to launch their attack, hence why Ilos, not being in the Citadel records, was spared. From the Prothean relic on Eletania we also know that the Protheans knew of Earth and humanity, probably documenting us in some way on the Citadel, meaning that the Reapers also had access to this information.

My point is that without the Citadel and its databases the Reapers may be sorely lacking information on galactic society, and attacked Earth not just because of Shepard foiling Sovreign, or their plans for a Human-Reaper, but because they knew about it and knew where to find it.