Murshidabad was vital for the Kolkata port as that is where Ganges enters into Bengal and split into Padma and Hugli river. If West Bengal lost Murshidabad to Eastern Pakistan then, then it would have lost control over the head water of Hugli. It could have compromised the well being of Kolkata port and Kolkata city itself. The overriding priority of Radcliffe was Kolkata as well as Congress lobbied strongly for inclusion of Murshidabad into India. Even if that means giving Eastern Pakistan a compensation like Khulna district. Khulna district had a bare Hindu majority of 51%, it was noway vital for the well being of Kolkata. So Khulna was a bargaining chip which the Congress leadership used to get the better deal.
On the other hand, CHT was given to East Bengal for 2 reasons-
1. As Radcliffe given Bengal's premier port kolkata to India, East Bengal was left only with Chittagong port. He wanted East Bengal's only port to have some buffer areas. And that buffer areas was CHT.
2. CHT was isolated from West Bengal, so contiguous majority principle for Partitioning Bengal could not have been applied for CHT. Plus, CHT had no transportation link with neighboring Assam province. It's only access was through Chittagong district. Radcliffe given great care to not to severe the existing transportation link with boundary. So it was only logical that CHT should be given to East Bengal. CHT had no strategic importance for India and had little or no economic value. So Radcliffe could favor this small gift to East Bengal knowing that he had given India the much bigger prizes.
Partition in 1947 was not a clear cut partition always faithful to the original premise of dividing the land according to majority religion. So a lot of Muslim majority districts were awarded to India which should have come to Pakistan, while some Hindu majority areas came to East Bengal as a compensation(always smaller than what was taken away). Buddist majority CHT was part of that bargaining. Why do you think, the concern of 2 lakh Bhuddist in CHT should get a special treatment when 11 million Hindus were stranded in East Bengal, 7 million Hindus and Shikhs were stranded in West Pakistan and 40 million Muslim were stranded into India by partition? CHT was a small part of a much much bigger scheme in hands.
So, do not cry foul. If any tribal in CHT do not like Bangladesh, he is welcome to migrate to his country of liking either in India or Myanmar. Radcliffe award is a done deal, a foregone closed chapter. There is no scope to dispute or challenge any of it's decision. Otherwise a Pandora's box will be opened.