# they caught him ... killed him

"they caught Ahaziah ... killed Ahaziah"

# they buried him ..."He is a son of Jehoshaphat, who sought Yahweh with all his heart."

"He deserves to be buried, because he was a descendant of Jehoshaphat, who tried hard to please Yahweh." 

# the house of Ahaziah had no more power to rule 

All the adult descendants of Ahaziah were dead, there was no one left to rule Judah.