How did dual thumbsticks separate movement and looking?

In this second episode of Hidden Levels, Amory traces the history of the humble-yet-genius joystick — from early 20th century aviation, to 1970s video game consoles like the Atari 2600, to the Nintendo 64 thumbstick in the 1990s, to what some consider the joystick's greatest implementation: the dual-thumbstick controller.

This optimal interface has changed the game, and not just the video game. The modern dual-stick controller is now considered an MVP in the military, and in medicine.