Allegorically Krishna represents soul atman existing in human body. In times of extreme distress, calamity and on a spiritual journey when Arjuna faced Kauravas in the battle of Mahabharata, his contemplation (chintan) on spiritual aspects of life was at its peak. And in those moments he finally reached state of enlightenment. It was then the entire wisdom of Bhagavad Gita was unveiled to him by Lord Krishna from within existing in his heart.
During Draupadi vastraharan the physical presence of Lord Krishna was not possible as Lord Krishna was never a physical entity. Something drastic and peculiar to notice here is, despite presence of maternal grandfather of Arjuna Bhishma Pitamah and Guru Dronacharya, Draupadi vastraharan happened and for this both Bhishma Pitamah and Dronacharya suffered badly.
As detailed in Bhagavad Gita by Lord Krishna everything in cosmic system is directly governed by laws of karma, as we sow so shall we reap nothing less or more. If Draupadi suffered at the hands of Kauravas it was all her doing. Dharmically it should not have happened but Kauravas never were follower of dharma (righteousness), prime reason why battle of Mahabharata took place. The war of Mahabharata is rightly termed as battle of Dharma.
As everything contained in Bhagavad Gita is allegorically, indulging in contemplation (chintan) we had to reach the underlying meaning. The instance of Draupadi vastraharan in Mahabharata indicates that unless human beings exercised control, used logic and exercised power of discrimination, war of Mahabharata becomes inevitable.
Ladies have been put on highest pedestal in Hinduism and all ladies on mother earth were daughters of God. Disrespecting ladies was not acceptable to God, prime reason why the Kauravas fared badly in war of Mahabharata.