Why there was west Pakistan army presence in East Pakistan, why wasn't a few battalions, rather a full East Pakistan army independent control and command was raised by the natives, local Bengalis.
And why was the bureaucracy, senior government officers from west Pakistan, Punjab mostly, this was one of the major cause of dissent and subsequent rebellion.
The East Pakistan locals would have stood firm in any warlike situation with India, the major concern.
In there stupidity, the measure that was taken to stop it became the reason for it actually happening.
Points to the fact that Generals are generally ignorant, narcissists, lacks farsightedness, lacks the empathy and doesn't know the ground reality.
The reason politicians are entrusted with this task.