The did not get the majority. They had allies to worry about. But Congress had majority seats in Parliament and states bordering Bangladesh for decades, and they allowed this infiltration. So did the communists. I don't think BJP is inclined to make them as their votebank. Only anti-national parties will recede to that levels. But you have a point. BJP should have made concerted efforts and made a strong case with it's allies when it was in the center. They failed to do it.
