Crazy people ruling an entire country, or even an entire empire, has a long and lamentable history dating back to the beginning of recorded time. Since human beings first gathered together to shelter from the elements it has been the most psychotic, paranoid or sadistic among them that seems to have an advantage in deciding who gets to be in charge.
Every era from the dawn of history to the present day has its share of maniacal despots who should be too wayward to hold down a job serving Slurpees, yet somehow rose to direct the lives of millions.
It could be that the characteristics that we find anti-social or terrifying in everyday life are advantages when it comes to being king, emperor or president. Or maybe the sociopaths in charge started out everyday Joes and were driven to the depths of bonkersness by the deeds required to achieve power. Perhaps acts of egregious insanity are sometimes the only way to retain power once it has been achieved.
Whatever the reasons, a dismayingly large proportion of the Earth's most powerful people have been hopelessly and destructively mad, with horrible consequences for everyone else who had to share the globe with them.