The argument isn't that the public is particularly good at choosing administrators, but that they have some ability to weed out bad administrators, and administrators have some pressure to perform. Unlike the public, they accept blame for the negative consequences of popular decisions like tax cuts or spending increases. The ability to take unpopular decisions is a feature not a bug.
One can make a similar theoretical argument that it is harder, possibly 'orders of magnitude' so for a CEO to determine the reliability of prospective hires to be accountable for decision making, and yet they invariably do despite greater ability to take executive decisions than the public