Any human being who realizes one’s true inner self, becomes a pure soul atman has nothing more to achieve in the manifest physical world. Such a liberated soul atman can only experience states of total bliss, ecstasy all the time.
Allegorically Krishna is soul atman existing in human body. In the battle of Mahabharata when Arjuna who had been indulging in spirituality suddenly realized his true inner self in the battlefield, his perception of life changed immediately. From a coward he became the rightful chieftain of Pandava army and prepared himself to fight the enemy Kauravas head-on.
Until Arjuna reached state of enlightenment, he was in a great dilemma, not wanting to fight his cousins, close relatives and friends and also his maternal grandfather Bhishma Pitamah and Guru Dronacharya. For an enlightened one all earthly bondages have already come to naught. For an awakened Arjuna realized that he would be fighting the manifest physical bodies not the soul atman. For a liberated soul atman, death carried no meaning.
If maternal grandfather Bhishma Pitamah and Guru Dronacharya sided with the enemy, they were bound to suffer the consequences, so surmised Arjuna.
For an enlightened one the meaning of life completely changes compared to masses, commoners.
When Arjuna himself became Krishna, an enlightened one there was nothing more to be learnt! Arjuna had finally reached pinnacle of cosmic life.
In the life of Mahavira, Gautama Buddha, Jesus Christ and Prophet Mohammed, the moment their Krishna awakened fully, they not only became enlightened but wiser in the cosmic journey of life. After gaining enlightenment at 42 years of age, Mahavira continued disseminating jnana wisdom so gained back to the community until 72 years of age when he left his mortal frame.
The statement where there is Krishna there is victory simply eulogizes the benefits of reaching state of enlightenment. It is an absolute fact of life that moment one gains enlightenment; one becomes a Krishna in real life.