Islam comes into it just as british are brought into it to explain harmful effects of colonialism to understand the relative under development. Europe succeeded because of 3 things, science, printing and freedom to criticize, India was the pre eminent place for new math and astronomy, it allowed freedom to criticize, atheists existed in India till the coming of Islam. Ramanuja , was the second greatest theologian in last 1500 yrs possibly and he stood against caste discrimination and so did many others in past 1000 years. Without Islam to worry about, people would have possibly be worried about these issues instead. Atheists existed in India for longer period than entire history of christianity thus far or the entire peak period of greeko roman civilization. To understand the influence of Islam, one only needs to wonder, what would have happened to western civilization had it been occupied, its universities destroyed, oxford and Cambridge being replaced with taj mahal and qutb minar. It was knowledge that changed the west and it would have been knowledge that would have changed India too, and knowledge production under Islam in India was bad.