Because of it's design, the NV 25 was the most advanced GPU of it's time. It also happened to power the Xbox.

Real world, the Xbox could push 125 million pollys per second. Using a backbuffer at 60 FPS, that equates to about 2.1 million pollys per frame. Two vertex shaders and a per pixel shader were all built into the silicon, which means that you don't take any performance hit when you use them. Shadows are calculated live with no impact to the frame rate.

So while the 733 mhz CPU may as well have been stock (and yet, still twice as powerful as it's competitors), it was the GPU that made the Xbox shine.