Greed is a motive, but I think fitzgugh was just scared. The aricara were out and a danger. I don't think they thought Glass could live, but wanted nature to take its corse and didn't want to kill him them self. They took his stuff because you wouldn't leave it with a dead man. Maybe Glass was hypotensive and near coma, and then thier big guilt was not burning him as they were paid to do. May have thought him dead or so near it didn't matter. Several wrighters mention then how quick animals dug up the dead, and it was useless to bury people.