The circumstances of Jammu & Kashmir's accession to India were unique. There was nothing in the British partition plan that said Hindu Princely States should accede to India, and the Muslim ones to Pakistan. That is why Jinnah accepted the accession of Junagadh to Pakistan in September 1947, never mind that a popular uprising undid that decision.

In the case of J&K, leaders like Sardar Patel expected the state to go with Pakistan, but Jinnah & Co overplayed their hand when they spooked Maharaja Hari Singh by instigating a tribal invasion of the state. With the invaders approaching Srinagar, Hari Singh reluctantly to acceded to India to enable the Indian Army to come in to fight the tribals.