Mostly incompetent bosses

Most senior people at Amazon are external hires and not internally promoted through to higher positions.

Also, this is clearly a butt kiss culture. People stealing credit people for other people's work and ideas to gain favor with their senior bosses is the only way people get ahead. And most people just won't do that kind of evil so they leave.

Even worse, I had over 15 bosses rotate through my department in my 2 1/2 years at Amazon. I respected exactly three of them, which is sad. Those three actually could do the job they were being paid to do. The rest were incompetent to the point of just doing whatever they could to force others to do their jobs, since they were mainly coming in from outside of the Amazon culture and they just can't do the job.