User blog comment:Tiredman2/Mass Effect Plot Holes and Contradictions/@comment-1388547-20120822072018

That is a bit odd. The best explanation I can think of was that it was set aside as some sort of reserve world -- Council property, to be held for later use -- and the Council decided that now was the time to allow it to be developed. That strains belief, though, because it seems like it's in a really good location near the Citadel, so other races should have been clamoring for access before humans entered the galactic scene. Maybe it's not so convenient as it looks? It might be in the same cluster, but actually far away from the Citadel or any mass relays. It is hard to fit this in, though.