Quick question, what exactly are the checklist tasks prior to evacuation and how long to do them? 90 seconds sounds a long time to throw a few switches
But more to the point, the crew up front have no idea what things are like behind why didn't one of them go take a look? (Or indeed take charge of the evac)
It seems a slowness to react to things characterises the mishap, which need not be a finger pointing blaming but like Sully said something to consider as part of the whole investigation
Delaying the evac that long (if that is the case) is not 'ok' or acceptable.. one look out back and they'd see the engines were not there making any worries over 'running engines' of little point, or maybe the whole checklist?