Massimo Graubart

Another major reason was cultural and linguistic suppression. Bengali language and identity were constantly sidelined, starting with attempts to impose Urdu as the sole national language. Over time, this created deep resentment among people in East Pakistan, who felt their identity was under threat.

When the Pakistani military launched Operation Searchlight, targeting civilians, students, and intellectuals, the conflict turned into a fight for survival and independence. India later intervened due to the refugee crisis and regional instability, which led to the creation of Bangladesh as an independent nation.

Economic inequality also played a huge role. East Pakistan generated a large share of Pakistan’s export revenue (especially through jute), but most of that money was spent in West Pakistan. Infrastructure, military spending, and development were heavily biased.

So in short, the war happened because of denied democracy, cultural oppression, economic exploitation, and military brutality—all piling up over decades. A good detailed historical overview is available here:
https://www.britannica.com/event/Bangladesh-Liberation-War