Yeah I think it’s complicated, India is a good example of this. So the concept of Purdah wasn’t really a “thing” before islamic invasions, yet once rulers were doing it more and more women got shoved into purdah (by this I mean the veil as well, it’s mobile purdah imo) as people aped the ruling classes. Some language/art was absorbed but the ruling classes weren’t big enough to overwhelm the culture/language and religion of the entire area, especially since they never ruled all of India. It was too big, Iran is similar in that it was just too much of a challenge to change the language and culture of the entire region.
People converted because they were poor or because they were trying to get in with the boss and some would have converted because they genuinely want to and many were basically forced. But abrahmic religions are so vastly different from eastern religions that it’s hard to see the attraction. It’s complicated to explain but a lot of it comes down to the idea of afterlife. To someone following an eastern religion the reward is the complete abscence of desire whereas in islam the reward is to have your desires met. Philosophically opposite ends of the spectrum.
I just think the way we talk about conflict in the middle east just ignore the fact that for a lot of people in the world religion is really real, the beliefs are very closely held. The extremism you see in India of some members of the Hindu majority reflect this as well, they really believe.
The secular west struggles with this so don’t know what to do in the face of religious extremism because they don’t really believe that people are motivated by religious belief, it must be because of something else. It’s why people just turn a blind eye to it because it’s difficult to comprehend when you don’t have burning faith yourself.