Why did God change His approach to humanity after the Tower of Babel?
Because false religions, pagan religions, and idolatry arose at the Tower of Babel, God had to do something totally different. He allowed the human race from Adam to flow like a river, and from that river He called Abraham, bringing forth the nation of Israel, the Jew.
Les explains that after Noah's Flood, 200 years passed until the Tower of Babel, where the nations made their appearance and God separated them by confusing their languages. Then another 200 years went by, and as a result of the false religions, pagan religions, and idolatry that came in at the Tower of Babel, God had to do something totally different. He let the human race coming from Adam simply flow like a river, and out of that river of humanity, with the call of one man named Abraham, came the appearance of the nation of Israel, the Jew.