Why did the Indian National Congress fail to convince Indian minorities to support united India

1. I don't think we should give full credit to the British for the 'divide and rule' policy. They could very well have been giving in to the popular demand those days.

For e.g. This was Sir Syed Ahmed Khan's speech in 1888

Now, suppose that all English, and the whole English army, were to leave India, taking with them all their cannon and their splendid weapons and everything, then who would be rulers of India? Is it possible that under these circumstances two nations — the Mahomedans and the Hindus — could sit on the same throne and remain equal in power? Most certainly not. It is necessary that one of them should conquer the other and thrust it down. To hope that both could remain equal is to desire the impossible and the inconceivable.

src: http://www.columbia.edu/itc/mealac/pritchett/00islamlinks/txt_sir_sayyid_meerut_1888.html

As Sir Syed says, it was 'inconceivable' that a Hindu could rule over Muslim or vice versa.

2. Even though British officially ruled for 90 years, the idea of 'India' was very new and might as well be very alien. There were small kingdoms everywhere, Tamil Nadu/Kerala itself had 3 or 4 kingdoms within themselves, it would've taken a radical visionary to think of a unified India. Even then, it would have been very difficult to think of the borders within which this mythical country 'India' would rise. Why was Ceylon, Burma, Nepal not part of India. Why was Sikkim included and Bhutan excluded? The nationalist fever gained legs only after world war I and frankly we just went with what British thought of as India. Just like how Celyon was administered separately, if the whole of South India was administered separately right from the start, we wouldn't even see the difference.

On the question of why INC couldn't convince muslims to be part of the same British administrative region that was called India, INC was overwhelmingly filled with upper caste hindus and brahmins. They tend to believe in speeches from people like Sir Syed than listen to INC for obvious reasons.

Muhammad Ali Jinnah was the founder of Pakistan. He started of as a strong Indian Nationalist. However he was disturbed by the comparative backwardness of Muslims in Big Business. Jinnah, like the Turkish economist Timur Kuran, identified the cause of as Islam's Inheritance Law. His own community was exempt from it and had done well. If reforming the Religious Law was impossible, then an alternative was the creation of a Muslim state where non-Muslims would have a lower status. The 'poet-prophet' of Pakistan, Iqbal- also a Nationalist originally- came to believe that Hinduism was based on the Caste system and thus Hindus could never embrace Socialism. Thus he thought separation from the Hindus would be beneficial for ordinary Muslims. Liaqat Ali Khan, who represented the younger generation of Muslim 'barristocrats', had a different perspective. By the time he returned to India, it was clear that Indian politicians, not British Civil Servants, would have their hands on the levers of power and patronage. However, so long as elections were held periodically, people like himself would not enjoy the sort of feudal power they had traditionally possessed. Liaqat saw that if the Muslim League created Pakistan by saying 'Islam is in danger' then it could keep a monopoly of power by simply repeating the slogan. He himself, once in power, showed no eagerness to hold elections and only lost his throne because he was assassinated. The case of Zafarullah Khan is more tragic. He was an Ahmadiyya and viewed the struggle for Pakistan as part of the founder of his sect's mission to restore Islam to its early glory. By the time he died, his sect had been classed as non-Muslim. One final point- non-Muslim minorities in Muslim majority areas quickly understood that their lives and property were not safe. Thus, there would have been an exchange of population even if some sort of Federal solution had been put into effect.

In Indian political thought there were two basic competing organizing theories, rather simply called The Two Nation Theory and the single Indian nation theory (or Greater India).

The basic idea behind the single nation theory is that Muslims and Hindus and many other religous communities as well are all intertwined alongside various languages and religous communities into one larger cultural unit. The idea behind the Two-Nation theory is that Hindus and Muslims, due to various prohibitions against cultural exchances like intermarriage, are essentially two separate nations. Most (but not all) adherents to this theory feel that India should be for Hindus exclusively and Muslims should have their own countries.

It isn't too hard to see why the Two Nation theory is more attractive to Muslims. It offers them the chance to live in a country where they run things. All the single nation theory offers them is a perpertual life as a minority in a country dominated by Hindus.