The main culprit behind the genocide that took place during the Partition was Mountbatten. From the time he reached India in March to the press conference of June 4th, it seemed to many that the only aim that he had in his mind was to get out of India as soon as possible. Sooner he leaves India, the sooner he will get his prize of becoming the First Lord of the Admiralty in Britain which he longed for his entire career. Several historians and writers have mentioned about Mountbatten's abject failure in understanding India and the affects of the hasty withdrawal. His spontaneous decision during the June 4th press conference to move the date of withdrawal to August 15th, 1947 (which was orginally set for June 1948) shows his clear disregard of the consequences that millions of people would face as a result.

“The date I chose came out of the blue. I chose it in reply to a question. I was determined to show I was the master of the whole event. When they asked: had I set a date, I knew it had to be soon. I hadn’t worked it out exactly then—I thought it had to be about August or September and then I went to the 15th of August. Why? Because it was the second anniversary of Japan’s surrender.” - Mountbatten

In his book "Disastrous Twilight", Major General Shahid Hamid writes:

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Here's an interesting blog post by Shoaib Daniyal about Mountbatten's culpability in causing the Partition riots:

https://thetimesofbullshit.blogspot.com/2013/08/the-villain-of-partition.html