Just speculating here, but perhaps there was a party very interested in destroying data on their infrastructure. Maybe to erase evidence of wrongdoing, or something else entirely.
That appears to be the case. The post says that hacking into all of these systems required access to multiple passwords, and because of the speed with which the systems were destroyed, I would guess the attacker had them all in hand to begin with.
that's where my thoughts went as well... Seems it could have been a revenge attack or coverup for something/someone else.