I agree with Prakhar Dixit

The choice of the parliamentary system was one political party’s decision and of course the only political party that was calling all the shots then was Indian National Congress.

The decision was taken in the summer of 1946, during a Congress party meeting, and then shepherded through the Constitution-making process as a party directive.

The Congress had formed an expert committee under the chairmanship of Nehru in preparation for the Constituent Assembly, and in its meeting of 15 August this small panel decided that independent India would have a British-type government. (The Framing of India’s Constitution by B.S. Rao, Universal Law Publishing, Delhi, 2006, Vol. 1, P 331)
( I am quoting from an article that has appeared in the Print website here).

At the time, neither Ambedkar nor Patel was in favour of a strictly parliamentary system. For that matter, neither was Mahatma Gandhi nor Pakistan’s founder and All India Muslim League leader Muhammad Ali Jinnah, although they were not involved in the framing of our Constitution.

When the Constituent Assembly began its work at the end of 1946, the Congress Expert Committee decisions became the recommendations of the Union Constitution Committee, also chaired by Nehru. But the Provincial Constitution Committee, headed by Patel, came up with a different plan. (Constituent Assembly Debates (CAD), 27 June 1947).

Nehru’s committee wanted a typical parliamentary structure of a unitary state with an indirectly elected Executive. The two committees held a joint meeting on 7 June 1947 and decided to have independent state governments, with governors appointed by states, not the Centre. As for the Executive, the joint committee decided to have a parliamentary-type system, but one elected ‘on the basis of adult franchise through a special electoral college.’ (Minutes, Joint Meeting, 7 June 1947, Rao, Vol. 2, P 609)