They were unnerved.

As in all cases where large bodies of men are put in imminent peril of death, whether by shipwreck, plague, fire, or violence, numbers were swayed by a mad panic of utterly selfish fear, and others became numbed and callous, or snatched at any animal gratification during their last moments.

Many soldiers crowded round the fires and stood stunned and confounded by the awful calamity; many broke into the officers' marquees and sought for drink, or devoured the food which the rightful owners had left when the drums beat to arms.
St.Clair Resolves on Retreat.
There was but one thing to do.

If possible the remnant of the army must be saved, and it could only be saved by instant flight, even at the cost of abandoning the wounded.

The broad road by which the army had advanced was the only line of retreat.