Why does Polaris reliably hold its position against the apparent motion of other stars?

It lies almost directly on top of the north celestial pole.

Polaris maintains its position because it happens to be situated almost precisely along the projection of the Earth's axis of rotation extended into space. This extension defines the north celestial pole, which is the stationary point around which all other Northern Hemisphere stars appear to circle. Because Polaris is located so close to this pivot point, its path across the sky during one night is negligibly small, making it appear fixed relative to the constantly moving background stars. This precise alignment is the fundamental geometric reason for its perceived immobility, which has made it invaluable for centuries in determining geographic North.