I've been a C-suite executive, and I've worked with executives (incl. CEOs) at public companies.

Not only is there often a thermocline of truth that stops "bad" information going up the chain, CEOs more often than not make decisions based on nothing but their own opinions, and they will more than happily discard any information that doesn't already fit that opinion, and even if negative things do manage to reach them from the other side of the thermocline, they often discount it or explain it away