You are too simplifying the politics of then 1970/71 blaming Mujib for every trouble. Yahya Khan should have convened the National Assembly on March 25, 1971 in Dhaka and let the elected members talk and debate on issues. Instead of waiting for their quarrelling there, Yahya took an unilateral decision to crack down in East Pakistan with machine guns.
Do you guys think Pakistan Awami League with a thin majority would have been able to pass any legislature to grant autonomy to east Pakistan? It needed a 2/3rd majority to change the then status quo. Yahya acted too early with too much of force that finally broke Pakistan into two.
India itself was not an issue. Issue was the three top leaders including Mujib. They were bickering among themselves and India took advantage of the situation. We ourselves in the east had no other recourse to resist machine gun fires than to seek Indian help.
No brother I am not ignoring the role of Bhutto or the military junta's role. I have acknowledged their mistake of postponing the National Assembly meeting which was scheduled for 3 March. Neither the military junta (apart from Yahya) or Bhutto wanted Awami League in power. They had reasons to distrust him because of the India factor. Mujib had given West Pakistanis sufficient reason to believe that he was India-friendly and this would have impacted on the foreign policy which West Pakistan and the Army desired. (Remember, Bhutto won seats because his election campaign was on an anti-India platform and that is also why he attracted the military junta's support.)
Then there is also Mujib's own admission in a private session with his party members in 1970, which was recorded by intelligence agencies, where he said his aim was to establish Bangladesh and tear up the LFO after the elections when no one could "challenge" him. He also referred to "outside" help (presumably Indian). This tape recorded statement was shown to Yahya Khan in the presence of his Bengali adviser Gholam Wahed Chowdhary but Yahya Khan did nothing because of his incompetence. Mujib should have been disqualified from contesting the election then and there.
When they announced that assembly postponement on 1 March the Awami League usurped the government's authority in the province which in itself was an act of treason and their militants started attacking non-Bengali Muslims, West Pakistanis (civilians and soldiers) as well as loyalist Bengali Muslims (who did not support the Awami League). There are testimonies (in the book "Blood and Tears") which mention the involvement of EPR in these atrocities even before 25 March.
Yahya did still come to talk with Mujib in mid-March and the Awami League by then was openly talking of Bangladesh while Mujib may have been talking of confederation (this had also been Bhutto's idea) as a last minute thought. The government also believed that Mujib (who had appointed Colonel Usmani as Commander) and that the Awami League in particular had planned a mutiny scheduled for 26 March. That is why they launched Operation Searchlight to pre-empt that mutiny. The objectives of the Operation were to restore the government's writ over the province which the Awami League had usurped and disarm Bengali policemen and soldiers. The atrocities were never an intended objective of the Operation.
Dhaka University was targeted because some of its dormitories had been insurgent training centres and arsenal depots. Of course, atrocities were committed during that entire Operation in Dhaka. The soldiers over-reacted due to the pressure they were under in the previous three weeks. And then it spiralled out of control on both sides. West Pakistani and East Pakistani soldiers turned on each other and also committed atrocities against each other's civilians. Tragic. (Although I will note here that some Bengali officers remained loyal to Pakistan till the very end).
It was ultimately a mix of our errors and the insincerity of a large part of the Awami League. But would any of this have happened if the Awami League had not espoused Bengali nationalism and won the 1971 elections with thug tactics against its opponents in East Pakistan? There were other parties in East Pakistan which remained loyal. Even some Awami Leaguers defected to the government's side when Operation Searchlight started.
The crux of the issue was ideology.
How could West Pakistanis been expected to feel comfortable with a party which believed in Bengali nationalism over two-nation theory? For instance, even if PPP was also confined to one wing like AL, it was at least cross-provincial. It won votes across Sind and Punjab and united Pakistanis across ethnic lines. Punjabis voted for a non-Punjabi - a Sindhi. Bengalis who supported the Awami League were talking in exclusive ethnic terms (i.e. "we are majority so we should rule") and West Pakistanis did not like this kind of thinking. Especially Punjab. Despite being majority in Pakistan today we still don't think in terms of "we Punjabis are ruling the other ethnic groups" because Punjab itself is an inclusive and hetereogenous province where anyone is welcome and can identify himself as a "Punjabi" regardless of his actual ethnicity.
For example, I am a Kashmiri while PM Imran Khan Niazi is a Pathan of Punjab. There are also large Sindhi, Baloch and Urdu-speaking populations in Punjab. There is no collective consciousness among Punjabis that we are one ethnic group and that we must rule others or exclude them. We ourselves are welcoming and inclusive in our own province. And I think that was the issue from day one for why Bengalis never understood us. They were homogenous and we were heterogeneous. (This was also the cause of the language movement in 1952 - which was a separate issue but sprung form the same factor of misunderstanding West Pakistan and Punjab's heterogeneity)
And we also didn't have an issue with Bengalis who did not support Awami League or the other pre-secessionist parties. (Remember Awami League still only won 42% of the total Bengali electorate). Maybe if Awami League was not allowed a free hand for years by our own government, they would never have become popular in East Pakistan. This was also what Professor Syed Sajjad Hussain says. Our own central government for many years allowed Bengali nationalists and leftists and communists to use all our official organs and media to spread hate propaganda against West Pakistan, suppress facts, exaggerate economic problems and spread their ethnic nationalist ideology against the two nation theory.