Fortunately, intelligence is a thing that goes steadily out-of-date as time passes. Also, once you know something has been compromised, you can take steps to significantly mitigate the damage.
I don't believe it, because I work in IT for decades and by now, above a certain level of confidence, the only way for vital information to be shared with wrong recipients can't be accidental. Years-long "accidental" proceder couldn't go unobserved. Too many people involved, too many IT-relevant security measures in the action.