Isaiah 47: 6-7
6 I was wroth with My people, I have polluted Mine inheritance, and given them into thine hand: thou didst shew them no mercy; upon the ancient hast thou very heavily laid thy yoke.
7 And thou saidst, I shall be a lady for ever: so that thou didst not lay these things to thy heart, neither didst remember the latter end of it.
God was angry because His people had strayed–again–away from Him into idolatry. His people were defiled by idolatrous practices, so he allowed Babylon to conquer them and take them into slavery. But Babylon went too far. They showed no mercy to the Israelites. They even placed heavy workloads on frail older people who could not stand up under such demands.
Babylon thought she would always be supreme among the nations (I will be a lady forever), and in her pride, she forgot that she was dealing with the Holy One of Israel.