Boards of private companies or public companies with $168 billion market caps?
Private companies, sure. Boards of private companies often have an iron grip on shareholders and are often unaccountable. But the boards of public companies need to worry about shareholder activists, hostile takeovers, shareholder lawsuits. The margin of error to keep outright stupid, corrupt, nepotists is much smaller on large public company boards.
High intelligence is rarely a requirement. Maybe most aren't stupid, but more are more lucky than they are particularly smart.
A non-trivial number of boards have run great companies right into the ground, or at least been too stupid or cowardly to stop it from happening.