Answer:
Because to them partitioning Bengal was akin to breaking up their motherland and it would benefit the Muslims
Step-by-step explanation:
The partition of Bengal received a hostile reaction from the Hindus because Bengal was a very large and great province and they felt that breaking it up would not only rupture India but also that it was a tactic by the British and Muslims to diminish the authority of the Hindus. They were also against it as East Bengal would then have a majority of Muslims where they would have more authority and no longer fear the powerful Hindu landlords.