Although what, you ask? Although… the guy the speaker shot was probably a lot like the speaker himself.
Here the speaker imagines a life for the man he killed, and it wasn't much different from his own. He guesses that maybe the other guy enlisted (that's where that strange word 'list comes from) because he was out of work and needed a job (which is why he sold all his traps, or personal effects), probably never imagining that this one choice might lead to his death.
And all of a sudden—poof!—there goes the speaker's reason for killing this guy. Foe? Hardly. He's just another guy, trying to make a life for himself out there in the big bad world.
We've got a lot more dashes peppering these lines, which helps us remember that this is a spoken poem—that we're actually listening to a guy try (and fail) to work out his role in a violent war.
Here, the dashes make it sound like he's spitballing—just listing possible scenarios for this dead man's life.