Why did God tell Abram to leave his father's house and his kindred?

Les teaches that the command in Genesis 12:1 follows the Lord's earlier word in chapter 11: Abram was to get out of his country, from his kindred, and from his father's house. Les explains there was a reason: Abram's family were idolaters, idol worshipers, and pagans who had no knowledge of the one true God. Out of the then-known world saturated with pagan worship, God put His finger on one man, appeared to him, spoke to him, and told him to leave his idolatrous family, make the break from paganism, and go to a land God would show him. Les also points out that Abram was not totally obedient, and he puts the blame on Abram's father rather than Abram: when Abram told his father he was leaving and did not know where, the old father said they would go with him, and Abram could not tie him down or lock the door on him, so he went. But God stopped him halfway between Ur and Canaan until his father died.