In the previous birth, Rushabha Dev had tied a net on the face of a cow and he did the sin of starving the cow, so the previous Karma was the cause of this incident.
At the end, Shreyans Kumar had got a special knowledge of knowing previous births. He knew that Rushabha Dev wanted food to eat. So he gave him the juice of Sugarcane and Rushabha Dev broke his fasts. This day is known as Akshaya Trutiya from that time.