Churchill famously said "Democracy is the worst form of government, except for all those other forms that have been tried from time to time"
Actually, what is wrong with democracy is exactly the same as what is wrong with all the others. If the ruler is incompetent, the state will fail.
Maybe some watery tart threw a sword at you. Whatever your justification for ruling, either you serve the people or notice too late that they have more swords than you do.
Even in the case where your ego is in check and you are the most enlightened prince whoever sat on a throne, the genetic laws will cause the next bum to perch there to be as enlightened as, well...any bum.
Like monarchy, susceptible to hereditary stupidity, only by committee.
No matter how much money you have, you will always convince yourself that the person who wipes your bum is overpaid. Then you will pay them less. Eventually they will stop.
You had to seize power to protect your country from its enemies. How does always happen that its enemies are its people? If you kill enough of them, the economy breaks down and then you can't afford those really big hats that make you look so generalissimoish.
Rule by the will of God. Usually means that God favours the least scrupulous since, after all, you wouldn't do that nasty shit to the penitents in God's penitentiary if the Holy Spirit wasn't telling you to.
Of course we know there is only one God because His Will always turns out to be the same. A new Mercedes and fresh women for the clerics and new and fresh suffering for everyone else.
Seems to come in different flavours. All of them screwed up by money or religion or money or ideology or money.
All decisions made by referenda. Will 'o the Uninformed Wisp. Imagine rule by consensus of the internet.