>>96577821
While violence is the supreme authority, you have a sub-caveman understanding of how that actually works.
When it comes to establishing rulership, it's not about individual acts of violence, it's about the ability to do mass violence. It's also about, nominally, the ability to PREVENT mass violence.
The best way to make sure that you have a monopoly of violence is to have the loyalty of as many violence doers are possible. There are many ways to do this, but they're generally going to involve skills that aren't "being the best at killing" and will tend to be things like "being the one who's best at leading people" or "being the best at organizing people."
And then it just comes a question of math.If it takes 5 of us to take down the local wizard, and we have 20 men, that means that we can probably kick that wizard's ass pretty fast.
Now this isn't to say that royalty won't have magic in them, probably. If magic is a heritable trait (IF), then some of those leaders of men are probably at some points going to start thinking "hey maybe we should start getting some of our relatives hitched to wizards." But again, this assumes that magic is heritable.