BD won the 1971 election and was the rightful ruler of the whole of Pakistan.
Why hold an election and not respect the results!
W Pakistanis wanted to rule over the majority and BD'shis were having none of this and so seceded.
See if Pakistan accepted the 1971 election result, both countries would now be much better off. BD probably would have spent the 1970s and 1980s creating a more fair and equal society and then would have prepared the ground for an eventual peaceful split by the year 2000, with economic relations intact. I am sure that there was also a possibility of a mutual defence pact as well against India in this scenario.
Like I say BD would want a full and unconditional apology for 1971 as otherwise relations cannot be normalised.