Walk two moons why did sals grandparents move to lewiston Idaho?

In "Walk Two Moons" by Sharon Creech, Sal's grandparents moved to Lewiston, Idaho, to be closer to their daughter, Sal's mother, who had left their home in Ohio. They wanted to support and maintain a connection with her and their family. The move represents a desire for familial bonds and the importance of being near loved ones during challenging times.