The only people that weren't able to come to Pakistan in 1947 were people who couldn't migrate: they were mostly belonging to the lower class of society; there were a few people (belonging to the upper class of society) that had too much invested in India to leave.
Post 1947, that left a huge vacuum in India, as most of the middle and upper middle class muhajirs migrated to Pakistan; and the mostly lower class Muslims were left behind in India. They lost their influence in UP and Bihar, and started getting ghettoized.
I'm trying to understand, what campaign promises has Modi fulfilled since getting into power?