The problem of being too great of a leader

In history, it has shown how great individuals such as Genghis Khan and Napoleon had changed society for the better almost single handedly( with their great allies/Marshals/Generals). But the problem with so much competence is that the moment you die, no one will be as competent as you, or those who are competent are dependent upon you, and without you, they pretty much are left not knowing what to do. It's not only about competence or greatness, but also future thinking. Most great men are far seeing idealists who were able to pragmatically integrate their ideas into society. But once they die, their supporters who aren't able to see how far or understand the intricacies of your work, eventually destroy all the work you have established. There are some instances where a competent ruler would be replaced by an equally competent ruler, such is the case of Phillip II of Macedon who was replaced by his son Alexander the Great. But when Alexander died, his empire fell to ruin. Similar case is that of Otto von Bismarch. Despite a staunch conservative, he was pretty liberal in terms of handling foreign policy and such. He succeeded in uniting Germany, but as he foresaw, Germany would be ruined after 20 years following his death. For Genghis Khan, he had competent successors, but they weren't as competent or smart as he was, and the Mongol Empire would cease to exist after 2 centuries.Although their legacy would live on, their work would usually be lost, or integrated but not as good as it used to be. I guess the best way of creating a lasting legacy is to train a capable successor, but there is a problem to this. If we read on the life of Marcus Aurelius, also known as the philosopher king, and the last great emperor of Rome, he trained his son Commodus to be a great emperor like him, but that turned out to be counter productive, and that cause the faster fall of Rome instead of the prosperity of it. Another case is that of Louis XV, the son of the great sun king, Louis XIV. He was trained to be a great king like his father, but rather than leading France to greatness, he led it the opposite way, which his son, Louis XVI did the same in turn. So the solution is instead force a tradition where the successor would strictly be that of merit and not nepotism, and only the ability of the successor would be measured, and of course, also how the successor acts and thinks. Since forcing your someone to be a king simply because he's your son could backfire, since they would have tremendous pressure on them, and are most likely denied basic pleasure from birth. Better let someone who wants to lead who is also capable of leading do the leading. But here also comes another problem : the leader may be meritorious, but he can eventually be corrupt. This happens when he is so competent that he could get away from being corrupt. This is where the hard part comes in. The citizens themselves must be competent and smart. This is so they can monitor the leader, in case he become too arrogant or corrupt. But that is why leaders are corrupt, because the masses aren't informed or smart. That is the great question of the day. If we the civilians are kept ignorant by other or ourselves, and we refuse to take the responsibility of gaining some power so we can also be responsible for our lives and others, then we are doomed as a species. Leaders should only be the most Competent, not the only competent one. If we are able to break the cycle, then humanity would prosper more in a decade than in a millenia prior to it. But then again, this would most likely lead to a revolution.