Isaiah begins to explain why the Lord had forsaken his people. They had done several things which were abominable to the Lord.
1) ‘they be replenished from the east’ means that they had looked to neighboring nations to save them from their enemies when they should have been putting their trust in the arm of God to win their battles.
2) ‘hearken unto soothsayers’ means they had begun to listen to the astrologers of their day—the soothsayers and sorcerers instead of listening the prophets of God who had been sent to them to lead them and call them to repentance.
3) ‘they please themselves in the children of strangers’ means that they had begun to commit adultery with the pagan nations around them. This often led to the pagan practice of idolatry.