> The problem is that those are two highly correlated data points. Toxic bosses are eventually found but at that point they leave a track of dead bodies.

Agree, and this is often overlooked. There's a handful of people I used to admire whose tendency to readily believe whatever's being sold by their middling middle management chain has left me deeply disappointed.

Middle management is a necessary evil, but there's little hope if upper management fails to recognize and subvert its inherent incentive structure.