Yaravam did not die in the days of Aviyah! Aviyah became king in Yaravam's 18th year, and ruled three years, and his son Asa became king in Yaravam's 20th year!
'Rashi', Malbim: He did not die immediately. He began waning due to the wars, and died later. Radak ? Hashem struck him in his wars, like verse 15 says that Hashem struck Yaravam and Yisrael in front of Aviyah and Yehudah; (not all of them died)! He died in lowliness; he had no strength from when Aviyah became king.
'Rashi', Radak, Malbim, all citing Bereishis Rabah 73:5: Hashem struck Aviyah, and Aviyah died 1 .
Radak citing Bereishis Rabah 73:5: This was a punishment for taking Beis Kel and not destroying the idolatry in it; he found there one of the golden calves. Others say that it was because he shamed Yaravam in public; he said "with you are the golden calves [that Yaravam made for gods]" (verse 8). This is farfetched. (Others there say that it was for causing that the widows cannot remarry (refer to 13:17:1:2) or for disgracing Achiyah ha'Shiloni; he is included in "va'Yikavtzu Alav Anashim Rekim Bnei Veliya'al" (verse 7).)
