וַיַּ֣עַן אֵלִיָּה֮ וַיְדַבֵּ֣ר אֲלֵיהֶם֒ אִם־אִ֤ישׁ הָֽאֱלֹהִים֙ אָ֔נִי תֵּ֤רֶד אֵשׁ֙ מִן־הַשָּׁמַ֔יִם וְתֹאכַ֥ל אֹתְךָ֖ וְאֶת־חֲמִשֶּׁ֑יךָ וַתֵּ֤רֶד אֵשׁ־אֱלֹהִים֙ מִן־הַשָּׁמַ֔יִם וַתֹּ֥אכַל אֹת֖וֹ וְאֶת־חֲמִשָּֽׁיו׃
And Elijah answered and said unto them: ‘If I be a man of God, let fire come down from heaven, and consume thee and thy fifty.’ And the fire of God came down from heaven, and consumed him and his fifty.
Akeidat Yitzchak
Israel/Yehudah's sin was in worshipping any of the aforementioned, all of which are quite powerless by themselves. Achav was a prime victim of these cults because his wife Izzebel had persuaded him. He taught these cults not only to his family, but to the nation. His son Achaziah practiced this folly in even greater degree than his father. This brought about the encounter which forced the prophet Elijah to destroy several groups of fifty soldiers each by calling down fire from Heaven to kill them. (Kings II,chapter 1) Since Achaziah sent three times a group of fifty soldiers instead of increasing the size of the troop contingent each time, there must have been a deeper significance in the number five or multiples thereof.