How was Babruvahana able to defeat Arjuna whom many Kaurava warriors couldn't defeat together in the Virat war?

 

How was Babruvahana able to defeat Arjuna whom many Kaurava warriors couldn't defeat together in the Virat war?

Babruvahana was son of Arjuna and Chitrangada, the princess of Manipura.Arjun left Chitrangada and Babruvahana at Manipur so that Babruvahana could ascend to the throne later. Both Babruvahana and his mother started living with Uloopi(Arjun’s snake wife).Uloopi was also a teacher of Babruvahana.

During the battle of Kurukshetra, on the 10th day, Arjun put Shikhandi in front of himself and attacked Grandsire Bhishm. Arjun struck Bhishm multiple times and later Pitamah fell struck by hundreds of arrows. The battle stopped to pay respects to the Bhisma . Even the Gods gathered in the skies to shower flowers on the fallen hero. Among the Gods were the seven Vasus, the brothers of Bhishm. They were angry by the unfairness. , They went to their mother Ganga, and said that Arjun must be punished - let him be killed by his own son. Ganga said, so be it. Uloopi(one of Arjun’s wife) was present and she was distraught. She denounced the curse and said that much more heinous crimes had been committed before and during the war. She pledged that she would revive her husband when the time comes.

Long after the battle of Kurukshetra, Yudhishtira decides to conduct the Aswamedha Yaga. The yaga horse enters the dominion of Manipur, Arjun thought that this was the country where his son Babruvahana ruled and hoped that he would come out and fight like a warrior. But, Babruvahana came out in order to welcome his father. Arjun told Babruvahana that his behaviour was not in accordance with the kshatriya tradition and that he must fight. This took Babruvahana aghast - how could he fight his own father? But Uloopi came to him and said that it was his duty to do so.

The battle begin. Arjun fought hard. But he could not defeat Babruvahana. The Vasu's curse ordained death to Arjun from his son. All other sons of Arjun had died during the war. So Arjun could not seriously wound Babruvahana but nonetheless hurting him terribly. Babruvahana started getting angrier. Using a weapon learnt from Uloopi, he shot an arrow straight at Arjun. Arjun fell down dead.

Babruvahana realized what he had done. He too fell unconscious out of grief. Meanwhile Chitrangada learnt the news of battle and rushed in. There she saw her husband dead at one end and her own son unconscious at the other. Uloopi was standing aside looking grim at the scene. Chitrangada rushed to Uloopi. She knew that Uloopi has magical powers. She reminded Uloopi's love for Arjun and begged her to save him. But Uloopi remained unmoved. So Chitrangada declared that she, her sister, will also end her life at the side of her husband.