How to go from chief executive to chief envisioner

Let’s do a thought exercise. If the role of the chief marketing officer is to oversee marketing and the role of the chief operating officer is to oversee operations, while the chief financial officer’s responsibility is to safeguard the organization’s finances, then what’s the responsibility of the chief executive officer? Surely, it’s more than overseeing executions or leading executives, yet the “CEO” naming convention doesn’t give much insight as to what the role is or what it’s responsible for.