The actual Pakistan Movement was formed by 2 Pashtuns and 2 Punjabis with the first relevant discussions of a separate country emerging out of Islamia College, Lahore in 1915 - roughly 60-70 years after the British had largely completed their conquest of modern-day Pakistan.
The original Pakistan Movement did not see religion as the sole reason for independence, but instead, as one of three reasons for the basis of Pakistan.
They saw ethno-cultural, historic, geographic, etc... affinities just as important as shared religion for the development of a national identity and national cohesion. Hence why, they advocated for Bengali and Hindustani Muslims to have their own separate countries instead of having them join Pakistan (which is why Bengal is not a part of the Pakistan acronym that was developed by the original Pakistan movement).
They saw "India" and the "Indian identity" as artificial constructs of the British and loathed British attempts to impose these identities on them.
"India, constituted as it is at the present moment, is not the name of one single country; nor the home of one single nation. It is, in fact, the designation of a State created for the first time in history, by the British. It includes peoples who have never previously formed part of India at any period in its history; but who have, on the other hand, from the dawn of history till the advent of the British, possessed and retained distinct nationalities of their own."
"This was a destructive power victimizing men and nations, crippling religions and states, enslaving at least half of the continent of Asia. With the coming of the British it had manifested itself in the establishment of the Indian National Congress. The motive of this Congress was to establish an All India Federation. The congress had designated all British possessions in South Asia as India denied to the non Indian nations the right to their own nationhood, and, by making pretentious claims, stamped Indian nationality on the peoples of this area." ~ Rehmat Ali on what he referred to as "Indianism" and the "Indianization" of South Asia.
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Also to claim that Punjabis and Pashtuns have nothing in common except Islam is just nonsensical. Our regions and ethnic groups are strongly inter-connected whether it be by genetics, geography, history, culture and much more.
This book excerpt sums it up well.
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Ethno-nationalism will continue in this country for as long as we look to Islam as the only sole pillar of our national identity.