The “risk” is based on alternatives and what gaining a reputation as a failure if you join a sinking ship at a company going through CEO’s quickly does to your future prospects.

These boards want proven superstars for many reasons and there’s a limited pool. Basically suppose you’re faced with a choice between a low risk CEO position that pays 5m/year you could do for the next 10+ years at a stable company and Intel who is most likely going to dump you. How much are you asking Intel per year, and how much do you want if they decide to terminate your contract for failing at achieving unrealistic goals in an unrealistic timeframe?

Those golden parachutes are often the result of an overly friendly board, but in some cases they are more easily justified.