GREAT WARRIOR WITH SHORT LIFE
Abhimanyu was born with Chandra amsa. Chandra promised to share his amsa in the shape of Abhimanyu for 16 years only. That is the life span of Abhimanyu.This Krishna knows fully, so he allowed Abhimanyu , while in the womb of his mother to hear and understand ONLY the breaking or entering Padma Vyuha or chakra Vyuha and interfered from Abhimanyu hearing the rest about the knowledge of Exiting from that.Krishna did this willingly knowing that Abhimanyu is destined to die in the Padma Vyuha.
Most personalities on the Pandava side like Panadavas themselves, ther army chief Drustadhyumnudu, Krishna ( himself a poorna avataara ) and many are were born with divine amsas.Similarly in anticipation of the Great war , Moon was requested to give His TEJAS or amsa for the War in the shape a Royal figure.Instead Chandra ) moon ) said;
”Abhimanyu is the reincarnation of Varchas, the son of the moon god. When the moon god was asked to let his son incarnate himself on earth by the other devas, he made a pact that his son will only remain on earth for 16 years as he could not bear to be separated from him. Abhimanyu was 16 years old when he died in the war.
His son, Parikshit, born after his death, remains the sole survivor of the Kuru clan at the conclusion of the Mahābhārata war, and carries on the Pandava lineage. Abhimanyu is often thought of as a very brave warrior on the Pandava side, willingly giving up his life in war at a very young age.
So the age of Abhimanyu or the longevity of Abhimanyu was known to sri krishna.So soHE intensionally made the childs mother, Subhadra go into sleep so that she may not hear the exit procedure from Chakra vyuha.
Unless this happens Arhjuna will not come in full fire, with vengeance to fight, otherwise he was behaving somewhere in heart out of love for elders and gurus.
This is all a part of the Masterplan.