Melachim Bais 14:21

21 And kol Am Yehudah took Azaryah, who was 16 years old, and made him Melech in the place of aviv Amatzyah.

Melachim Bais 14:21 Meaning and Commentary

2 Kings 14:21

And all the people of Judah took Azariah
Called Uzziah in the next chapter, and so in the book of Chronicles; both names signifying much the same, the one "the help of the Lord", the other "the strength of the Lord":

(which was sixteen years old;)
yet as he began to reign in the twenty seventh year of Jeroboam, ( 2 Kings 15:1 ) and Jeroboam began to reign in the fifteenth yaer of Amaziah, ( 2 Kings 14:23 ) , he could be but four years of age, for the solution of which, (See Gill on 2 Kings 15:1):

and made him king instead of his father Amaziah;
which was after his death, and not when he fled to Lachish, as Kimchi thinks.

Melachim Bais 14:21 In-Context

19 Now they plotted kesher against him in Yerushalayim; he fled to Lachish; but they sent after him to Lachish, and assassinated him there.

20 And they brought him back on susim; and he was buried at Yerushalayim with his avot in Ir Dovid.

21 And kol Am Yehudah took Azaryah, who was 16 years old, and made him Melech in the place of aviv Amatzyah.

22 He rebuilt Eilat, restored it to Yehudah; after that HaMelech slept with his avot.

23 In the 15th year of Amatzyah Ben Yoash Melech Yehudah, Yarov‘am Ben Yoash Melech Yisroel began to reign as Melech in Shomron, and reigned 41 shanah.