It’s rather self-explanatory, but I’ll explain to make it clearer for you. The majority of India did not convert to Islam, it was just localized mostly to the parts that became Pakistan and Bangladesh. Not even close to the entire country. Why wasn’t India “Islamicized” like Iran/Persia, Egypt, Mesopotamia, Syria, Central Asia, North Africa, etc?
The politically correct answer is that like Medieval China, Medieval India was already too old and too populous of a civilization to have its indigenous religious traditions and social order completely uprooted by Islam (or Christianity, in the case of Medieval China).
What is the politically incorrect answer? Also, couldnt i say that zoroastrian persia was as grand and old of a civ as china/india and yet it was Islamized