Jinnah wanted partition, rightly or wrongly back in 1947. Let's bear in mind the massacres were Moslem on Hindi, Hindu on Moslem.... why, perhaps you can answer?
Before the British arrived, after the French and Portuguese settlements, the sub-continent was divided into a host of princedoms / regional powers, dozens of them; They were not one economy. ..... also, too, where were the borders of an area with hundreds of languages, a number of religions and, with the caste system (for Hindus)  something considered today rather primitive but which is still is an influence.. 
Now, today, India is a powerhouse, one unified, if you like, by foreigners!