What mistake did krakauer make with beck weather's that he would later regret?

Weathers is suffering the effects of an eye surgery he had years back. The lower pressure on the mountain was too much. He did not inform his guides of this. Krakauer knew that Weathers was in bad shape. Weathers insisted that he be able to have another go at the summit. Krakauer knew Weather's eye would not get better. Krakauer always regretted letting Beck Weathers go.