Why did Arjuna's horses and chariot burn in flames after the Mahabharata war ?

Answer 1

The Chariot and Horses of Arjuna were reduced to ashes upon Lord Krishna's abandoning it after attainment of Arjuna's objectives. -

After the Pandava army headed by Drishtadyumna and Shikandi retired to their tents, the 5 pandava brothers along with Krishna proceeded towards the camps of the Kauravas.

And they find empty tents and finally when the 6 reach the pavilion of Duryodhana, Krishna quickly tells Arjuna :
TAKE DOWN YOUR GANDIVA AND DISMOUNT IMMEDIATELY.
A puzzled Arjuna did as ordered by Krishna. After Arjuna got down from the chariot, Krishna released the horses and got down from the chariot. Interestingly now, the Anjaneya bannered flag disappeared also and in just few seconds like a flash, the ENTIRE CHARIOT BLAZED FORTH TO ASHES.

A stunned looking Arjuna and others were speechless and astonished by this development. Krishna replies to them :

Arjuna, this chariot , before had been consumed by diverse kinds of weapons. It was because I had sat upon it during battle that it did not fall into pieces. Already consumed by the energy of brahmastra and various other celestial weapons applied on you by Bhishma, Drona and Karna, . Now it has been reduced to ashes upon my abandoning it after attainment by you of your objectives.

Hearing the words of Krishna, Arjuna and others felt totally ashamed as their egos also got burnt . Arjuna was under the impression that it was his valour which singlehandedly won the war for Pandavas. Probably Almighty Krishna thought that he had to teach Arjuna some lessons as well ! -

Answer 2

Because there was no asbestos in those days.

Answer 3

My fellow Indian, I don't know.

Answer 4

it is said that the enemy released bhramastras, some type of ancient nuclear weapon

Answer 5

Fire.