Admiral ranks began as positions in the battle line

Did a monarch invent admiral rankings, or did they emerge from naval practice?

They emerged from fleet organization: the admiral commanded the center, the vice-admiral the van, and the rear-admiral the rear squadron.

The hierarchy grew from fleet formation rather than a monarch's arbitrary ranking scheme. The admiral directed the center and the whole force, the vice-admiral led the van, and the rear-admiral controlled the squadron at the back. Modern titles therefore preserve the spatial command arrangement of an age-of-sail battle line.