Tracing family roots establishes a person's authority and heritage. Ezra's genealogy reaches its ultimate peak by connecting directly to Aaron, forming a distinguished family tree that is, at least in part, a continuous line of High Priests.
There is a general consensus among commentators regarding the unique rank attributed to Aaron at the conclusion of this family record. His special designation serves a dual purpose. First, it confirms his elevated status as the High Priest. Second, it honors his historical position as the very first priest, the founding figure from whom all future priests descend.