I think it is double negative as “nobody” before “doesn’t” is supposed to emphasize the negation, not reverse it. With that the sentence is supposed to mean: “Only body that watches the show could have the slightest idea what that sentence meant”.
Such constructions are frequent in Russian, like “it is not true that I have not done nothing” but apparently people use them in English too.
I ain't no english major, but everyone I know in America uses the "Two negatives resolving to a positive" form of english [0]. I'm pretty sure Australia is the same as I actually had this funny code review a few weeks ago which involved flipping an if statement based on a triple negative which unsurprisingly caused a bug. One of the guys in Sydney approved it, then unapproved it because he thought the original if statement was right, then realized the fix was right and approved it again while commenting that we should fix this horribly confusing function.
Such constructions are frequent in Russian, like “it is not true that I have not done nothing” but apparently people use them in English too.