In very small businesses, the second-in-command is often more of a right hand to the CEO rather than a true COO. A startup might aspire to get big enough to need a COO but not get there for a while. When the CEO gets to a point where they realize they can’t do it all or don’t know how to do it all, they need a partner or mentor to assist them. The first second-in-command is often an MVP from within the business.