I can tell you what my Grandpa told me in his 5-6 years of being in East Pakistan !
He said that he felt a distinct superiority complex of the civil bureaucrats who'd been posted from the West ! And why ? Because they'd served under the Britis first and they brought with them the same colonial mindset...you can see their arrogance even now ! They won't come across as 'servants of the people of Pakistan' but more like their 'masters'. They behaved a little like how a 'grumpy school headmaster' would ! There wasn't an ounce of racial superiority complex between the People of the West and the People of the East ! In case of the civil servants because many of them were from the Punjab or were Biharis who had immigrated to the East because most of East-Pakistan's bureaucracy being Hindus had opted India instead of residing in Pakistan, the wounds of the partition were fresh because the Punjab had seen a lot of blood-shed and the Biharis had experienced quite a lot of it themselves. What this did was it created a sense of paranoia and distrust that could have been shaken up if there was greater people-to-people interaction but regrettably there wasn't partly because West Pakistani politicians were corrupt and preoccupied by other problems beset to Pakistan and partly because a 1000 km separating the two wings created a huge natural barrier to greater interaction. The East Pakistan intelligentsia certainly didn't help with their demand for 'Bengali' to be made our national language whilst all the other ethnicities (Pathan, Punjabi, Sindhi, Baloch etc.) had accepted Urdu as our national language in line with the wishes of the Quaid and understanding the wisdom behind choosing a non-partisan language like Urdu to be our national language despite it being spoken as the mother tongue by less than 9% of Pakistanis (now !). Then there was the politicization of this, the agitations, the perceived meddling of the intelligentsia sitting in Calcutta with their anti-pakistan stance and finally Mr.Mujib and the Agartalla Conspiracy ! These things compounded created such a volatile atmosphere that the differences became pronounced and the distrust and disunity between the two wings grew. Had we reached out to each other at that point in time to bury these differences and create a Pakistan based on 'federalism' as the Quaid envisioned it to be with each province having control of their own resources, their culture, their language, their people, their administration, their bureaucracy etc. with only a few portfolios like the Armed Forces and Foreign Policy being controlled by the Central Government or had Bhutto and others giving into some of Mr.Mujib's demands...we would still be one ! Instead we ended up instigating a crackdown that finally led to Operation Searchlight and the start of the '71 War.