It is a typical question usually all Sangh Parivar used to ask and that question is used to silence the Muslims, and haunts Muslims since independence.
Since the whole or majority Muslims did not leave itself shows that Pak was not a cause of Muslims.It was some "undersatnding" of the then leadership and Britain to divide the country.
ANd if you see, that country is not accepted or understood Islam as an ideology. That was just a mass hysteria created among North indian Muslims for some vested interests.
And FYI, an average Indian Muslims are more faithful to God than any Paki Muslim. Since they are more illiterate in Urdu and Arabic as well.It is from my direct experience.
Religion is just used as a mask to gain vested interests.