 Why does Moran think it could be beneficial if one of the crew members was killed on the alien planet?
From the viewpoint of the Nadine's ship's company, it was simply necessary to get rid of Moran. Now it lay astern, and Moran could see the planet that had been chosen for his marooning. The ice-cap, by its existence and circular shape, proved that the planet rotated at a not unreasonable rate. A water-ice ice-cap said that there were no poisonous gases in the planet's atmosphere. The fact was verified by the thick, dense cloud-masses which covered most of the surface,—all the surface, in fact, outside the ice-cap. But since there were ice-caps there would be temperate regions. In short, the ice-cap proved that a man could endure the air and temperature conditions he would find. Moran observed these things from the control-room of the Nadine , then approaching the world on planetary drive. Two of the Nadine's four-man crew watched out the same ports as the planet seemed to approach. Without rigid control of space-travel, any criminal anywhere could escape the consequences of any crime simply by buying a ticket to another world. Wherever the yacht landed, such a disparity between its documents and its crew would spark an investigation. Moran, at least, would be picked out as a fugitive from Coryus Three. The process would be to find a planet and check its climate and relationship to other planets, and its flora and fauna against descriptions in the Directory. If they left a beacon, they may have left an identification of the planet. "I think," said Carol, to Moran, "that if it's too tropical where this signal's coming from, we'll take you somewhere near enough to the ice-cap to have an endurable climate. If somebody were wrecked on an even possibly habitable planet, the especially developed seed-strains would provide food in a minimum of time. Moran wondered, momentarily, what sort of world they came from and why they had revolted, and what sort of set-back to the revolt had sent the five off in what they considered a strategic retreat but their government would think defeat. His victim would not be mourned by anybody, and somebody formerly in very great danger would now be safe, which was the reason for what Moran had done. Moran had needed to get off-planet, and fast. But space-travel regulations are especially designed to prevent such escapes. He surrendered, stipulating that he wouldn't be landed back on Coryus; he still clung to hope of avoiding return—which was almost certain anyhow.
 He and the remaining crew members could pass security clearance with only five members on board.
 He would be more likely to survive an attack from the Nadine crew if they ambushed him.  He could convert their body to nutrients, which he could use to survive longer on the alien planet.  He and the remaining crew members could pass security clearance with only five members on board.  He could steal the deceased crew member's identity and use it to start a new life on a new planet.