My read[0] suggests it's a combination of religious, political, ethnic and economic issues, which are all inherently social things. From the causes of the splintering into 2 countries to what's happening today. And social issues crop up when the needs of some group in a society aren't being met, because they aren't being properly heard. I've seen things in the news about Modi; he doesn't sound like the type to listen to/heed anyone not in his circle.
It is generally extremist arms interested in destabilizing India to strengthen other regional powers (usually Pakistan).
The goal of much of these terrorist attacks simply end with ... no India, not "we demand change to policies in a reasonable way"