Because the Lord loved you, i.e. because it pleased him to love you; it was his free choice, without any cause or motive on your part. Compare Deuteronomy 10:15 1 Samuel 12:22 Psalms 44:3.
Related Commentaries of Deuteronomy 7:8
Deuteronomy 7:8
8 But because the LORD loved you, and because he would keep the oath which he had sworn unto your fathers, hath the LORD brought you out with a mighty hand, and redeemed you out of the house of bondmen, from the hand of Pharaoh king of Egypt.