"Once words are spoken, they are like water spilled; naturally, there is no way to take them back. Especially with something as significant as the succession of the throne, one cannot treat it lightly.
Since the decision has been made, no matter how others may try to persuade him, Franz is not prepared to change his mind.
Anyone can grow weary of a job after doing it for years, and the Emperor is no exception. Though power is enticing, after holding it for over fifty years, Franz had long lost his initial passion.
One could tell from his actions over the past decade or so, delegating a substantial amount of state affairs to Frederick, ostensibly to "train the Crown Prince's political skills," but in reality, it was to slack off.