Some of them are longstanding family businesses (monarchies), perhaps they have delegated or divested some of their ownership to a board or to the public to some degree (spectrum of semi-democratic monarchies).
Some are private companies with a single leading founder (different kinds of revolutionary/military dictatorships). Some act like large enterprises, that may be democratic or meritocratic to some degree internally, but closed to the public (single-party regimes).
It's interesting to think that we spend the majority of our time (work) quite happily within such power structures.
I guess the rather obvious trick is that it works as long as a company does not get a monopoly on violence. That's the difference.