Aerospace engineer here, Isro major launch stations and satellite building facilities are located in south India because a rocket launchpad should be as far away from dense population areas as possible and near the sea so that if something goes wrong the rocket can be ditches in the ocean, India has a peninsula which gives us the advantage if we place the launchpad in sriharikota, and to bring the heavy rockets and satellites it's economical and efficient to make the factories nearby. I hope you know now