The others—they abandoned the sick? But Captain Crozier said—that must have happened after the mutineers captured him.

[ Harry might not have much faith in people in general anymore—and not much left for, say, Lt. Little, who it seems rewarded Crozier's confidence by failing to appear as hoped for—but he's fairly certain that Crozier would have never abandoned the sick, least of all Jopson, if he could at all help it. ]