Final answer:
Rob Hall is disappointed when he passes Krakauer at the Hillary Step because Krakauer refuses to communicate with him.
Step-by-step explanation:
Rob Hall is disappointed when he passes Krakauer at the Hillary Step because Krakauer refuses to communicate with him. This indicates a breakdown in teamwork and communication between the two climbers. The disappointment stems from the fact that Hall expected support and cooperation from Krakauer, but his refusal to communicate creates a sense of isolation for Hall during a critical and dangerous part of the climb.