Synonyms for “idiot” : fool, half-wit; imbecile; dolt, dunce, numskull
And, in researching this, I was surprised to find that “numskull” was not spelled “numbskull”. Look at me; ever learning. Thanks Houghton.
What you found are contemporary, modern meanings of the word. The word in its Greek root (taken over into Latin), idiota, simply means someone uninformed, uneducated. It did not in itself mean stupid or mentally deformed etc.
Brooks is not stupid or retarded. He’s just sadly uninformed, naive. Idiot. Poster-boy for idiots around the world.