God showed Ezekiel four scenes of increasing abomination (a deeply offensive act). In each scene, the people of Israel were worshiping false gods inside the Lord’s temple.
Jerusalem’s defilement (moral and spiritual uncleanness) was complete. Idolatry (the worship of false gods) took place in many parts of the temple. Different groups of people were involved. They worshiped different gods. These gods came from many foreign cultures.
This was not one small sin. It was a mixture of many false religions brought together in one place. One abomination was added to another.