For whatever reason (someone curses him, Harry chooses to, etc), shortly after the Battle of Hogwarts, Harry is sent to the past and ends up in America. With no way back he (officially?) gets a new identy: Percival Graves. With that he finishes his schooling at Ilvermorny and builds up a life away from being the Boy-Who-Lived.

And then his capture and captivity end up being similiar to that of Moody and Harry just can't get over 'falling into that same damn trap'.