There is a key difference between a dictator and a monarch, and that difference is stability:
There are many differences between Hitler and Frederick [the Great], but perhaps the key one is stability. Frederick, while not intrinsically secure from his foreign enemies, was quite secure from any domestic opposition. No one was trying to kill him; no one could have accomplished anything by killing him. He was, in short, a monarch. A dead monarch is replaced, automatically, by another monarch — the identity of whom is already known. If the old monarch was assassinated, God forbid, the new monarch is generally not the assassin (or his employers).Not so for a dictator! People were trying to kill Hitler all the time, and it’s a Satanic miracle that none of them succeeded. If, say, Elser’s bomb had worked, it would have changed the course of history. There was no Hitler 2.0, or vice-Hitler, or Son of Hitler, waiting in the wings. Hitler, for all his faults, was one of a kind. Thus, the incentive was considerable.
And thus, Hitler — unlike Frederick — has to devote considerable effort to shoring up his sovereignty, which is by no means secure. He has to scapegoat the Jews and fight the Communists, for instance; his sovereignty depends on his popularity, and he is popular because he fights these popular enemies.
And, as we already know, it’s better to live under a stationary bandit than a roving bandit.