The purpose of assigning one person to a task is NOT that the assignee has to do it all or know it all. The purpose is to have a single point of responsibility

The purpose of assigning one person to a task is NOT that the assignee has to do it all or know it all. The purpose is to have a single point of responsibility that oversees things and get it done. Assigning to multiple persons without clearly dividing responsibilities is doomed to fail. And what's worse, when the task failed, people point fingers towards each other and no one wants to take responsibility.