It could be a lot of things.
Here’s a short article on the narcissistic boss. It’s a personality disorder, and one that causes a lot of problems in the workplace. Notice these two traits in particular: insistence on being right all the time; can’t handle confrontation. Sound familiar?
Could also be poor selection of management candidates, an ineffective leadership training program, and a decades-long implicit message from executives and managers that ethics are important as long as they don’t get in the way.
Could be the engineer/scientist personality. The skills and personality that make a good engineer and scientist are very distinct from the skills and personality that make a good manager.