Why does Krakauer's first attempt to climb Devil's Thumb fail?

On the third day, just as he approaches the most dangerous and intimidating part yet, a snow storm breaks, and he loses all visibility. He twice almost falls into crevasses, and it takes him the entire day to make it through the dangerous icefall. Soon after, he reaches the place where a pilot is supposed to drop his food to him, but the unending snow means the conditions are too poor, so he just has to keep waiting as his supplies dwindle