As far as I understood, the rad tech told the RN that they were unable to monitor patients after receiving sedation. Knowing this, she pushed the medication and left. If I (or one of my CRNAs) was doing a case in radiology, we would be expected to stay with the patient the entire time after giving sedation.
I can't comment on the cases that you mention as I do not know all the details, but I'm guessing none of them led to bad outcomes (better to be lucky than good, as they say). All I can say is that it sounds like a setup for disaster. The only times I ever push sedation myself outside of an OR is for blocks (Where I am physically present for several minutes), or as the RNs are about to wheel the patient to the OR (when I know that they'll be in the OR in a matter of minutes. Even on the way over, the nurses are watching them, so they're not completely unmonitored).
I will concede that there are many cases that could easily be prosecuted criminally but aren't, or why the nurse in this case wasn't charged in a civil court. I'm not entirely sure why. Maybe it has to do with the medicolegal climate in certain states vs others. Maybe it's because it's ridiculously difficult to sue RNs (it's usually docs who take the fall for nursing errors, as it would be if a CRNA made a mistake under my name), so the natural course was to take a criminal charge. I honestly don't know the circumstances. All I can say is, since it did go to criminal court, that based on the circumstances of this case, the prosecutor was able to make a reasonable case for negligence.