There was a reason, but the reason was insane. Hitler actually believed his handlers that there will be a peace treaty between Nazi Germany and British Empire and that he will get the British colonies as the spoils of war.
The complete story of Rudolf Hess is still under wraps.
Yes....Rudolf Hess’s flight to the UK still remains one of the great mysteries of WWII. Was Hess insane or was he on a mission sanctioned by Hitler? Hess’s behavior at the Nuremberg Trial would seem to indicate the former and it also probably saved him from the hangman’s noose as well.