That which has taken place, had been ordained. It was the destiny of those great warriors. Krishna allowed it to take place although he was fully competent to befell it.
भवितव्यं तथा तच्च दिष्टमेतन्महात्मनाम्॥ उपेक्षितं च कृष्णेन शक्तेनापि व्यपोहितुम्।