Hanging an Italian CAVALRY division unsupported to cover a 30 mile wide sector wasn't really smart, either....
Basic German Doctrine was to flank, surround and reduce. Paulus wasn't the wisest of the battlefield leaders,either...
It was Romanian sectors that were hit and overrun, no?
Paulus had an abundance of artillery ammo but was terribly short of rifle ammo. As the circle grew tighter around his riverside positions, the airlift that did get through didn't bring in more personnel, it delivered 88mm rounds and some minimal food and took out critical, party political and wounded personnel. His infanty force had been reduced by hunger and the weather to very limited rifle and mortar fire. Foraging for food and seeking to avoid death by freezing consumed more of their collective efforts than battlefield tactics and contact.