I will respond first from my training and experiences in personnel management outside of scuba. I was trained in various forms of what people call "creating a culture of continuous improvement." It assumes that participants want to improve and will thrive in a nonjudgmental, coaching environment focused on making everyone all they possibly can be. I have been part of such an environment at times, and I thought it worked great.The "instructor" should have had his credentials yanked long before this fatality. He'd been reported many time before (going back ~10yrs) for a laundry list of poor diving, instruction and business practices. The one I recall the most was a 2016/2017 era money/instruction drama which was widely discussed on RBW. The entire concept of the scuba industry "policing" their own through agencies and insurance (so the government won't step in like they do in France and Quebec among other places) is just a complete lie. I don't care about @GLOC 's just culture in cases like this. Brian's instructor should have been in jail for fraud long before a student died.
Looking back on my career, though, it only works great in an environment in which that ideal attitude is spread throughout the group. It runs into trouble when you have what some people call a "bad apple." There really are people who are not interested in doing the best they can. There really are people with no interest in improving. There really are people who want only to game the system for their own personal benefit. As I type, the images of such people I knew both as colleagues and subordinates are flashing through my mind. Unfortunately many management systems are set up solely to deal with such types, and the truly virtuous majority suffers. On the other hand, those evil individuals absolutely must be dealt with effectively, but they rarely are, especially when they find themselves in the friendly, coaching environment I just described. They can destroy such an environment. The old adage of one bad apple spoiling the whole barrel has a strong foundation in truth.
I will return to the world of scuba for an explanation. A number of years ago, a ScubaBoard poster described an instructor's practices that were truly horrible. He tried to be evasive, just asking if things were really as bad as they seemed, without identifying that instructor. He gave enough clues, though, that a couple of people (including me) figured out who it was pretty quickly and then confirmed it with the poster privately. One of the other people who figured it out was on the Board of Directors for the agency, and he brought the situation to their attention. What happened? Nothing. As I understood his explanation, the board did not feel they could afford to lose an instructor. They needed all the instructors they could get, and this one certified a lot of students each year. Maybe they counseled him. I don't know, but the last I checked he was still teaching. When management encounters a bad apple, there is too often a practical reason transgressions are overlooked.