[wisty]

The big question - how did the judge know that what was divulged was actually consequential?

It can't be something that could just have sensitive parts redacted, or even something that could be described (i.e. the blueprints for a new weapon, a list of secret agent identities, or an analysis of likely targets).

It must be information thats mere existence is damaging, like "a video of our troops gunning down innocent civillians".

OK, in this case it was more benign - probably something about the US tapping into Israeli communications. But still, if they've done nothing wrong, what do they have to hide?