Hinduism is indeed the uniting factor for India
Regions that became predominantly Muslims got out of this United Hindu Kingdom like Afghanistan,Pakistan, Bangladesh etc.
Had Religion not a uniting factor,India and Pakistan would never have existed on the map of Earth but small ethnic based states with constant infighting with each other.
This region will one day become a super Power of this world like it was some thousand of Years ago.And religion will play major role in keeping these countries United.
There never was a United Hindu Kingdom.
There was British Empire, a de-facto secular state, governing vast territories all over the world, with South Asia as the largest Province.
British Raj split NOT primarly around religious lines, but around ethno-cultural lines.
- Myanmar (barman culture)
- Pakistan (Indus culture)
- Sri Lanka (Sinhalese culture)
- India (Gangetic+Dravidian culture)
This also explains why Pakistan further divided into TWO separate nations: Pakistan and Bangladesh.
The way i see it, the other ethno-cultural groups who remained in the newly independent India, werent either strong enough or clever enough to get their own full independency. Geography, as usual, is also factor in play.
Would it really be that surprising, if Tamil-Dravida area became a separate country after WW2? Or East and Bengal became one united separated country?
Why didnt it happen? Because Nehru and his colloborators were potlitically clever enough to stop that from happening.