I've read a book recently called [url=https://www.goodreads.com/book/show/51862863-a-declaration-of-the-rights-of-magicians]A Declaration of the Rights of Magicians[/url], where the background history of it basically manifests from something along the lines of...

Nobles kept power and Kings justfified Divine Mandate by being massively powerful wizards who fought in wars where magic was flung and shit. Got to the point where the abuses of dark magic (necromancy, vampire shit, mind control) made things out into a Dark Age that was ultimately resolved by basically exterminating anyone with a hint of having such potent powers and then suppressing the magic of commoners utilizing cuffs that burned their flesh in response to attempts at casting magic.

Nobility could totally persist in a world like that, where peasant revolutions are less like "they have the military on their side so it'll be a tough one, but we can power through" and more like "we're literally fighting Fire Jesus on his home turf; this is gonna suckkkkk". And you can toss in some good ol' noble eugenics to constantly breed bloodlines with high magic potential and voila, thar ye go.

And then our characters, who are basically the next generation of traditional Noble-Knight rules of the world, are the ones that have to grow up in a world where technology/magitech has finally caught up to the powers of their bloodline inheritance? Gonna take a bit more to puzzle things out though, because admittedly, the book that I read was set during the French Revolution, while this setting is a good bit beyond that.

...

On a side note, because I'm a sucker for drama, it'd be nice if the Noble-Knight pairings aren't set in stone. Have there be a process for swapping out one Knight for another Knight-student n such. Or have the opportunity to be a solo Noble or a mercenary-kinda Knight.