Nah, not really.
They're just harvesting humans because humans are apparently the greatest beings currently alive in the universe.
Although parts of that could just be because Cerberus is now a bunch of reaper puppets. I mean, that's kinda why they got those protheans. Not like there weren't other, more powerful races back then.
Granted some of them were robots, but still.
In any event, they clearly don't give 2 shits about one failed reaper attempt. With the population of earth they could make BILLIONS. Because apparently collectors fucking fail at life and were doing everything COMPLETELY WRONG.
Yeah, it's kinda stupid. But then again
so is much of the plot.