Diplomats who don't know what's really happening would be quite bad for the job they're given, considering what diplomacy SHOULD be about. Either corrupted, blackmailed, insiders or intentionally ignorant is a much more likely scenario, except for one rare case: If a genuinely good person is found as stupid enough to not realize what's going on, and lifted to her/his position for exactly that reason. In this case efforts would be needed from the criminals to keep her/him in the blind. Looking at this from the criminal point of view, it would seem risky.