Q. This isn’t a smart alec question, just something I wonder about. If Solomon was so wise, why did he end up following false idols?
A. Solomon broke a number of rules while he was the king, acquiring many horses and much wealth and thinking himself to be better than his subjects. But the one that resulted in his spiritual downfall is that he married foreign women from the surrounding nations. This was forbidden to Israelites (Deut. 7:1-3). Before he was finished Solomon had accumulated 700 wives and 300 concubines, which was also forbidden (Deut. 17:17).
As he grew older his wives led him astray and turned his heart toward their gods. They convinced him to build altars for their gods and to join with them in worshiping their gods. This so angered the Lord that he swore to tear the kingdom apart because of it (1 Kings 11:1-13). After Solomon died the northern part of the kingdom fell into idolatry and the nation was split in two as the Lord had promised.