Why didn't Karna use Vasvi Shakti on Lord Krishna who was the mastermind of all?

Why didn't Karna use Vasvi Shakti on Lord Krishna who was the mastermind of all? Karna can not use Vasavi Sakti as and when he wanted to. It was a conditional weapon that works only when conditions of Indra got fulfilled. Indra said. vidyamAneShu shastreShu yadyamoghAmasa.nshaye | pramatto mokShyase chApi tvayyevaiShA patiShyati || 33|| And if, maddened by wrath, thou hurlest this dart, while there are still other weapons with thee, and when thy life also is not in imminent peril, it will fall even on thyself.' Karna answered, 'As thou directest me, O Sakra, I shall hurl this Vasavi dart only when I am in imminent peril! Truly I tell thee this!'" Karna could use the Sakti only when his life is in danger and when all his other weapons got exhausted. So to use it on Krishna first,Karna had to fight with him using all his other astras. It won’t be possible since Krishna was not the warrior in Kurukshetra. He chose to drive the chariot of Arjuna but not to wield weapons. Technically speaking,as per Indra’s condition,Karna can not hurl Vasavi Sakti on Krishna directly. We observed what happened when Srutayudh hurled a mace of Varuna on unarmed Krishna. It killed Srutayudh himself. So Karna did not dare to use Vasavi Sakti on Krishna. Even If we take Arjuna and Krishna together countering Karna,then also Karna could not use it either on Arjuna or on Krishna because Karna did not fight a full fledged battle with Arjuna before 17 th day.So Karna could never hurl Sakti on Krishna in particular because of Indra’s condition. If he ignores that he himself will fall in danger. Kisari mohan Ganguli English Translation Vana Parva CCCVIII Bori Critical Edition Sanskrit version Vana Parva ch 294