Why does The author choose to reveal the family's reason for moving and the father's arrest so gradually? What is the effect on the reader when the reason becomes apparent?

I believe the author wanted us to learn the back story of the Japanese she was depicting before descending into the horrors and injustices of the camp. She wanted us to see that the Japanese Americans who were deterred were like all Americans..... their crime, the reason for their punishment, was the fact that they were Japanese.