I would say that one of the most profound elements of DiCamillo's work is the idea of restoring lost or misplaced relationships. There is an emotionally profound theme that is evident in the book that relationships between people are vivid and dynamic, and can be formed and reestabilshed in almost any setting. Everywhere the dog goes, Opal follows and forms relationships with new people. When the dog leaves, Opal is able to reestablish the relationship with her father. In the end, it is the dog and Opal's pursuit of it that helps to overcome her own sense of alienation and loss and fully grasp the idea that emotional relationships do not die and can be developed in nearly any condition. Perhaps its this quality that allowed the book to win the honor, as this lesson is something that can expans the emotional intelligence of any child.
The Newberry Awards are awards for books that make a significant contribution to American children's literature. Because of Winn-Dixie won a Newberry Honor (not the first place Newberry Medal) in 2001.
In my opinion, the book won because it is a book about a child who comes to be more sure of herself. She starts the book out as a lonely and unhappy child. As the book goes on, she becomes more outgoing. She also learns to be more tolerant of other people.
These are, in my opinion, sort of "hot topics" that tend to make books look good. I think that the awards people want books that will teach certain things. This book does that -- it teaches tolerance and self-reliance and self-discovery.