Why did agreements between the federal government and native americans fall apart

 Well, it is my understanding that it happened because the federal government didn't follow the agreements. They thought that the Native Americans were just a bunch of savages, and it was better not to follow the agreements to make sure that things would go the way the government wanted. 

Among the Native Americans, after several disappointments, the federal government ( in general the "white man" ) had the reputation of not following their own agreements, signed or not