Muslims who chose to migrate to Pakistan saw partition as an event of great self determination.
Well, actually, if you look at the demographics, you will realise that the reality is that there was a huge population transfer in the Punjab (around 5 million Muslims from East to West Punjab); a major one in the Sind (around 1.2 million), and some more from other parts of India. Perhaps another 1 million or so migrated from Bihar and west Bengal into east Bengal. I don't have a figure for the Urdu-speaking migrants, the Mohajirs, but today, Urdu-speakers are 8% of the population of Pakistan, I should imagine around 13 million.
Pakistan is certainly not made up of a flood of Indian Muslims leaving India and landing up in Pakistan. It was largely a transfer in the Punjab and in the east, Bihar and Bengal in, Bengal out.
In today's figures, after all, nearly 160 million out of the 175 million in Pakistan are 'original' inhabitants.
This is not to dilute the huge numbers involved, or the catastrophic human tragedy. It is just not true that when partition came, half the Muslims in India marched out. Many left, but nowhere near all. After all, there are 138 million Muslims in India, 10 times the number of non-Punjabi, non-Sindhi migrants to Pakistan.
Jinnah and the Muslim League weren't asking for a homeland for ALL Muslims, they were asking for a homeland for Muslims, two, in fact, in the north-west and in the east. Neither they nor anybody else expected the population transfers that took place (Gandhi may have been an exception).
It was never to have happened like that. The best that we can make out is that what was anticipated was the sort of 'partition' that formed Punjab, Himachal and Haryana out of the old Punjab, and MP and Chhatisgarh out of MP: administrative measures, not death and disaster on an epic scale.
Jinnah personally must have felt vindicated in some respects, but he had never wanted a moth-eaten Pakistan; he had hoped to keep Punjab and Bengal together, which, incidentally, would have prevented the transfers, most of them, and perhaps the bulk of the slaughter, and he had hoped that the two homelands would serve to keep majoritarianism in the other entity at a low level.
In brief, what happened in reality was beyond the imagining of anybody.