I assume they are confusing CEOs with entrepreneurs and investors.

It's a claim repeated very frequently around here when people criticize exorbitant compensation packages for execs.

For instance, see [0] below by fallingknife.

[0] https://news.ycombinator.com/item?id=35665329

That's not what that comment says, it says there are massive risks in REPLACING a CEO, it says nothing about risks the CEO is taking.

"the massive risk and uncertainty of replacing a CEO"

This is not what we're talking about. This is about risk to the company, not risk to the CEO.

"Essentially CEOs are able to hold the board hostage."

Exactly. There is no risk to the CEO. They hold all the cards.