1947, why Bengal divided?
When the British realized that Hindus are becoming very prominent in politics they tried to balance .in 1905 they tried to divide Bengal by act but disagreement and violence from higher caste Hindus made their attempt unsuccessful and finally, they withdraw the act in 1911. the higher caste Hindus never wanted Dhaka as a provincial capital. they were even against the establishment of the University of Dhaka.
If you find the literature of that time you will see prominent writers of that time(eg. Rabindranath Tagore ), who were mostly Hindus, did not write even one percent of their entire writings about the Muslims but they were more than sixty percent of the entire Bengal population.
Most of the landlords were Hindus who were reluctant to develop east Bengal and were transferring their wealth to west Bengal especially Calcutta.
So Muslims wanted their own land with the hope that it will make their living condition better. even many lower caste Hindus stayed in East Bengal as they thought it was better to stay with Muslims rather than be subjected by higher-caste Hindus.
So the bottom line is, though, in history, it was tried to establish that partition of Bengal was a wrong decision of English, but the fact is it was obvious due to huge socioeconomic difference between east and west Bengal at that time.
It was historical truth that most of the Muslims wanted their own land as they were fade up with their Hindu landlords and they wanted to say - enough is enough.