There is a very practical explanation for why a nautical mile equals one minute of arc on a great circle around the earth.
When doing celestial navigation (using a sextant) you are measuring the elevation of the sun, moon or stars above the horizon and then, combined with azimuth (compass) angles, you perform a series of trigonometry problems and chart (map) measurements to ascertain your location.
This work is made simpler by having a common measure underpinning arc (minute), distance (nautical mile) and speed (knot = 1 nm/hr).
When doing celestial navigation (using a sextant) you are measuring the elevation of the sun, moon or stars above the horizon and then, combined with azimuth (compass) angles, you perform a series of trigonometry problems and chart (map) measurements to ascertain your location.
This work is made simpler by having a common measure underpinning arc (minute), distance (nautical mile) and speed (knot = 1 nm/hr).