Read the history of Pakistan Movement. For no reason Kolkata eastern half was not allocated to east Pakistan. Kolkata was built with money from east Bengal. However, three big leaders of Bengal could not make unified approach about Kolkata and many others. The three leaders were A.K. Fazlul Haq, H.S. Suhrawardy and Khwaja Nazimuddin. They were bickering among themselves.
Anyway, Muslims of then Bengal were happy to see their east Pakistan materialized though its map was insect-eaten at the periphery.