The crew would have had very little indication that things were not right until they rotated & the aircraft did not fly.
Are you sure about that ?
Surely the PNF calling out rotate at a speed that was clearly insufficient would have rung alarm bells.
I can't believe they operate any ULH revenue routes where Vr could be such a low figure.
There are definitely some serious human factors involved in this, I cannot believe fatigue does not play a part.