This verse starts with an explicit he
(= Azariah). It means that his father started to subdue Edom, and he, his son Azariah, finished this work by making Elath into a strong(er) harbour city in Judah; see also 2 Kings 14:7 and the explanation of it. Another name for Azariah is Uzziah, and under that name we encounter him often in the Chronicles and the prophets.
22 Azaria rebâtit Elath et la fit rentrer sous la puissance de Juda, après que le roi fut couché avec ses pères.