What is the root cause of the Mahabharat war? Who in most responsible for this epic battle? 

For this you will get few answers. Some will say women like Draupadhi can be blamed as the cause. Some will blame the king Dhetrashtra. Some will blame even Krishn. I blame God. Yes Sri Bhagwan himself. Hindu scriptures are complex to understand but when they make sense completely then you come to one conclusion and that is there is nothing in this universe but God. So all our scriptures are his leela. Leela means divine play. So lord himself took human forms and came to earth with his devoted rishis and Sants and devtas and they all acted this out to reveal the great message of Mahabharat. This is why when barbarick the grandson of bheem was asked what he saw during the war and he said all I saw was krishn everywhere during the war. I saw nothing else.Just like the ramayan the Mahabharat is a leela performed by lord to lead humanity to salvation. This is the beauty of Hinduism. In the Mahabharat there is a wonderful line which says ahinsa parmo dharm. Which means ahinsa is the highest duty For Hindu. This is why you should see krishn in Arjun, bheem, hanuman, shivji, Parvati etc…. Bhagwan and his devotees are just acting out this leela nothing else. Otherwise no Hindu scripture makes any sense. Because the question always remains open about God otherwise because you wonder why God as krishn can’t stop the war, I mean after all of he created the universe then why can’t he stop a simple war. It’s because he is the player who does the acting and the producing and directing. Hope this makes sense.

Jai Sri Bhagwan