Don't know abot Marines but years ago in the Army a good conduct medal meant you were squeekie clean, so to say.
Not to make light of this Marines death but in the Navy we called it the not getting caught medal.
The Army good conduct medal is automatic now for any soldier every three years of service- if there has been no non-judicial punishment or letter of reprimand given to the soldier. In the old days, if you didn't get an Article 15, you wouldn't make a great NCO. Now, even one bad mark in your records can stop a career and get you forced (chaptered) out of the service.
I was actually surprised that the Marine Sergeant didn't have more awards- all those listed are automatically awarded for service in current operations - especially for an NCO.
In my opinion, anyone willing to sign the line is already a hero in my book. Especially those Marines.