Procedures were either not laid out or, more likely, they were ignored.
It is not just this, there have been a series of safety failures that should have been easily prevented if people had been doing their job.
Something is badly wrong.
I’ve been trying to figure out how the tank imploded and can only surmise that they draining the tank ( pumping the contents out) at a high rate of discharge and the vent on top somehow closed creating such a vacuum as to cause the sides to collapse inward and splitting the tank open. The sudden release of vacuum pressure them caused the material to backflush and spray outward.
Just a WAG.