The successive waves of Muslim armies penetrating into India followed much the same pattern. Leaders such as Mahmud of Ghazni and Muhammad Tughluq expanded Muslim political domains without altering the religious or social fabric of Indian society.
Because pre-Islamic India was entirely based on a caste system in which society was broken into separate parts, conversion to Islam happened in a step-by-step process. Often, entire castes would convert to Islam at a time. This would happen for many different reasons. Often, however, the equality Islam provided was more attractive than the caste system’s organized racism. In the caste system, who you are born to determines your position in society. There was no opportunity for social mobility or to achieve greater than what your parents achieved. By converting to Islam, people had the opportunity to move up in society, and no longer were subservient to the Brahman caste.
Buddhism, which was once very popular in the subcontinent, slowly died out under Muslim rule. Traditionally, when people wanted to escape the caste system, they would move to the major population centers and convert to Buddhism. When Islam became an option, however, people began to convert to Islam instead of Buddhism, while still leaving the caste system. The myths of Islam violently destroying Buddhism in India are simply false. Buddhists were tolerated under Muslim rule and no evidence exists that shows forced conversions or violence against them.
Wandering teachers also had a major role in bringing Islam to the masses. Muslim scholars traveled throughout India, making it their goal to educate people about Islam. Many of them preached Sufi ideas, a more mystical approach to Islam that appealed to the people. These teachers had a major role in bringing Islam to the masses in the countryside, not just the upper classes around the Muslim rulers.
Now I often think that when most of the people belonging to lower classes of the society converted into Islam then what else can be expected from them except being Mureed of Saeen, Chaudhry and Maulvi? When I think that then I am able to understand why there is feudalism and extremism in my country.