>>19227565It wouldn't get infested with maggots unless they buried it close enough to the surface for bug-types to get at. And since it's part Earth-type it's reasonable enough to assume there's enough dirt there to cover the corpse properly.
Nincada could POSSIBLY cause some damage as it's an underground-dwelling insect, but since it's not a meat-eater I doubt it'd be attracted to the decomposing Marowak-corpse.