Israel forgot God’s grace and left her first love, as did the church of Ephesus in, Revelation 2:4, “Nevertheless I have somewhat against thee, because thou hast left thy first love.”
Pride is in all of us. We who have nothing to be proud of are prone to take credit for ourselves for any success or “FAVOR” God bestows upon us. Forgetting, all we have is of God. So, Israel became vain and trusted in her own glory and beauty. The beauty which God gave her she used to draw attention to herself. The admiration and affection from the idolatrous nations from which she had been called to separation. Like an unfaithful wife she became filthy preferring others to her own husband. That’s spiritual adultery.
James 4:4, “Ye adulterers and adulteresses, know ye not that the friendship of the world is enmity with God? whosoever therefore will be a friend of the world is the enemy of God.”
Instead of turning from her corrupt ways, or even practice restraint, the pleading of the Prophets had the very opposite effect, she increased her wickedness. It shows how very low a people can get who turn their back on revealed truth & learned to love darkness rather than truth (LIGHT) because their deeds were evil.