Do I really need to read the thread for you? You seem to have two perfecly good eyes in that watermellon between your shoulders.
What next, should I bottle feed you too?

*sigh*
Allrighty. What can explain such shivan losses?
Either the shivans planned it or they didn't.
If the planned such loses, the question is why?
Maybe they are suicidal. Maybe it's some religious ritual. Maybe the left extra forces behind just to make super extra sure. Maybe the forces didn't want to leave.
If they didn't plan it what went wrong?
Calculation error? Missing component supplies? GTVA interference?