Sharp discrepancies between the account of Aviyam in Melakhim and in Divrei Hayamim lead to the conclusion that Aviya served God while concurrently tolerating other religious phenomena - an anathema to the worldview of Melakhim: zero tolerance for idolatry and hence absolute condemnation of Aviya. Assa, the next king, removes idolatry from Yehuda and reestablishes the covenant with God. However, when he perceives a military threat from the Northern Kingdom he turns to Aram for help and not to God. 

Courtesy of the Virtual Beit Midrash, Yeshivat Har Etzion