In every major terrorist incident, some thread always traces back to Pakistan.If this attack does trace back to. Pakistani soil then there are only two bad outcomes.If the ISI knew or assisted you have a cause for war. If the ISI did not know, you have evidence of a failed state where private armies launch invasions. Pretty bad either way.
if we go with this logic, isn't Oklahoma City Bombing or july 7th london blasts a proof of failure estates? coz in each case authorities failed to control their own nationals.