Literal translation
he is an idle onlooker like the moon
Meaning
he's a gawking, idle onlooker
Explanation
The expression names someone deeply naive, standing open mouthed before everything around them, like an idle onlooker who stops to gawk at a spectacle without grasping its meaning. Literally, es badau coume la luno translates as he's an onlooker like the moon: the comparison pairs badau, meaning a simpleton or an idle gaper, with the moon, a body that silently watches the earth without ever acting, shifting through its phases with a passive, somewhat absent constancy. The image also plays on the moon's traditional reputation for fickleness, the very source of the word lunatic, reinforcing the sense of a vague, detached contemplation of reality. The register is familiar, used with a touch of good natured mockery toward someone dreamy, distracted, or simply naive about the events unfolding around them, without real malice on the speaker's part.