Was something wrong psychologically with Lebron James in this series?

I have never seen Lebron this passive in my life. Lebron averaged 28 points against Boston, 26 points against Chicago, but only 17 points against Dallas. Boston and Chicago are better defensively than Dallas. He also struggled defensively as well. In my opinion, Miami was the better team than Dallas and should have won the championship, but Lebron James simply collapsed. I honestly don't know what went wrong.