From what I know of stuxnet, it was found after it escaped from the Iranian nuclear facilities. The virus was then dissected by anti-virus groups who reverse engineered it and discovered it was only exposed because the Israeli programmers made it too aggressive. They removed portions of it's stealth to insure it penetrated the target machines.
From my reading of the charges against Cartwright, he simply confirmed to an investigative author the facts of the stuxnet "Operation Olympic Games" mission. Stuxnet had long since done its work by the time Cartwright leaked to the author, David Sanger.
By then Iran and most computer egg-heads already knew who wrote it.
Prior to that point the word on the street was that it was Israel (alone)