Why did the Prophet of Bethel Lie?

Question: Why did the old prophet of Bethel lie to the prophet of Judah?  (1 Kings 13)

This question comes by way of Facebook. Why did the old prophet from Bethel deceive the man of God from Judah? This story comes from the book of 1 Kings, which is the original Game of Thrones, but without all the gratuitous smut. 1 & 2 Kings give us the history of the kings of Judah and Israel and show us what happens when a nation that forgets God.