Who was Elah in the bible

Elah the son of Baasha was a King of Israel who like his father practiced idolatry. The prophet Jehu had prophesied the end of Baasha’s bloodline which came to pass when Zimri assassinated king Elah and all the members of his family.
Zimri, one of his officials, who had command of half his chariots, plotted against him. Elah was in Tirzah at the time, getting drunk in the home of Arza, the man in charge of the palace at Tirzah. Zimri came in, struck him down and killed him in the twenty-seventh year of Asa king of Judah. Then he succeeded him as king.
1 KINGS 16:9–10
Sometimes it seems as if certain kings of Israel were so devoid of good that the Bible hardly goes to the trouble of mentioning anything about them. This must have been the case with Elah.
Elah was born to Baasha, who had assassinated Nadab, the son of wicked Jeroboam. By assassinating Nadab, Baasha was carrying out judgment on the family of Jeroboam for its wickedness, yet Baasha’s own family, including Elah, was also wicked. Just as Jeroboam had done, Baasha and Elah practiced idolatry and promoted it throughout Israel. As a result, a prophet named Jehu foretold the demise of Baasha’s family as well.
So while Elah was getting drunk at the home of the man in charge of his palace, one of his officials, Zimri, assassinated him and reigned for seven days in his place. Zimri also killed all the other members of Baasha’s family, fulfilling Jehu’s prophecy.
It is interesting that the small town of Gibbethon figures twice in the story of Elah. At Gibbethon, Baasha assassinated Nadab and usurped the throne. Years later, after Zimri assassinated Elah and usurped the throne, the people of Israel declared Omri king instead of Zimri while they were besieging the town of Gibbethon.