Why would someone who once kept the law begin to disobey?

Answer From The Annual Reading Schedule - Week 48 Notes For Deuteronomy: If their heart turned away (Deuteronomy 30:17). Here we are, trying to keep the law the best we understand, yet many around us trying to get us to break the law. Does not the Word show us that it is only if our heart turns away that we would not obey? Why then are so many trying to convince us to not obey? Do they realize they are teaching or trying to teach us to turn our hearts away from Yahweh? We cannot listen to them. They do not realize the sin they are trying to get us to sin.