According to Chapter 4 of the Sai Satcharitra, for what reasons do saints choose to incarnate on Earth?

Chapter 4 explains that saints take an incarnation on Earth not for any self-interest, but purely for the sake of others. They are described as being naturally liberated, yet they are always ready to uplift the distressed. Their advent occurs when religion is in decay, people have lost sight of the ultimate goal (Paramartha), and society is obsessed with worldly happiness from wealth, status, and family. Saints descend to this mortal world to protect the humble, poor, and weak, to destroy irreligion, and to awaken faith, thus restoring the chance for humanity's ultimate well-being.