Why Arjuna could withstand attack of many warriors, but Abhimanyu could not withstand and died?

 

Though Abhimanyu was equal to valour of his father Arjuna, he lacks the following on 13th day of the war, when he was encircled by the host of Kaurava warriors.

• Abhimanyu lacks the experience that Arjuna had in wars. In critical moments of war, experience does count.
• Arjuna’s bow Gandiva was given by AGNI. Gandiva was incapable of being injured by any weapon,ie., no body can break it.
• AGNI gave Arjuna Gandiva bow, apart from 2 inexhaustible quivers, ie., the arrows will get replenished in the quivers, automatically.
• In the war between Karna and Arjuna, it was mentioned that Gandiva had 100 strings and hence, even though Karna could break 11 bow strings of Gandiva, Arjuna was able to continue the war.
• Arjuna had a well experienced charioteer Shri Krishna, who saved Arjuna and the chariot, many a time during the war

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Drona himself acknowledged that he could not differentiate between the use of Gandiva by Arjuna and the bow by Abhimanyu.

I do not see that in battle there is any difference between the wielder of Gandiva himself and this one of great lightness of hand, filling all the points of the horizon with his mighty shafts.' Hearing these words, Karna, afflicted with the shafts of Arjuna's son, once more said unto Drona, 'Exceedingly afflicted with the shafts of Abhimanyu, I am staying in battle, only because (as a warrior) I should stay here.

As Abhimanyu had only one bow in his chariot and his bow was not indestructible, Karna, at the advice of Drona, broke that bow. And, others quickly deprived Abhimanyu of his chariot.

Karna quickly cut off, by means of his shafts, the bow of Abhimanyu, as the latter was shooting with great activity. He, of Bhoja's race (viz., Kritavarman) then slew his steeds, and Kripa slew his two Parshni charioteers. The others covered him with showers of arrows after he had been divested of his bow. Those six great car-warriors, with great speed, when speed was so necessary, ruthlessly covered that carless youth, fighting single-handed with them, with showers of arrows. Bowless and carless, with an eye, however, to his duty (as a warrior), handsome Abhimanyu, taking up a sword and a shield, jumped into the sky.