The two business, Krsna's. Because He has already explained, bhutanam isvarah. "I am the controller of all living entities." Therefore when there is discrepancies in the execution of dharma, then He is to punish and reward. Paritranaya sadhunam vinasaya ca duskrtam. Two things.
Lecture on Bhagavad-gita 4.7, Bombay, March 27, 1974