What changed Anakin was his separation to his mother, specially at that age, when he was already attached to her. Her murder at the hands of the Tuskens aggravates this further and pushes him further into the dark side. That's why we see Anakin at age 9, because at that age it is more difficult to let go of your parents. I experienced some of that because I stopped living with my parents (they stayed in central america) at age 14. This caused a great impact on me. However, at that age I was mature enough to adapt to the situation.