I just finished the book, "Unbroken" on Christmas Day.
I just received it from wifey for Christmas and have barely gotten into it....at this point in my reading, he's still a mischievous thieving laddy!
There is some speculation in the book that, his juvenile delinquent days in his youth, hard wired him to think he could do anything he wanted. His bother channeled his energy into running and he became a record-breaking runner and went to the Olympics. These traits stood him well in his efforts to survive and endure his inhumane torture and hardships later on.
Enjoy the book.