Jerusalem faces a harsh reality regarding her moral and spiritual decline. Rather than merely copying the behavior of her sinful sisters, Sodom and Samaria, she actually surpassed them in wickedness.
There are two primary ways to understand how Jerusalem's actions compared to those of her sisters. One approach views the comparison as a statement of extremes. Jerusalem did not simply settle for following in the footsteps of Sodom and Samaria; she went much further and acted far worse [רד״ק, מצודת דוד, ביאור שטיינזלץ]. In fact, this can be seen as an ironic wish from God, as if to say He wished she had merely copied their behavior and not committed even greater evils [רש״י].
Alternatively, the comparison draws a line between internal belief and physical action. In this view, a distinction is made between a person's inner faith and their actual deeds. Jerusalem did not adopt the complete loss of faith seen in Sodom and Samaria, who entirely denied God. She continued to believe in Him and maintained the service in the Temple. In practice, however, she committed the same terrible acts by blending idol worship into her religious life [מלבי״ם].
The concept of smallness regarding her behavior is understood in two distinct ways. Some view it as a measure of the sins themselves. To Jerusalem, the terrible crimes of Sodom and Samaria seemed minor and insignificant, prompting her to corrupt her own path far beyond what they had done [רש״י, מצודת דוד]. Others understand this smallness as a measure of time. Just a very short time after Samaria was sent into exile as a punishment for her sins, King Manasseh took power in Jerusalem and acted more wickedly than any leader before him [רד״ק, ביאור שטיינזלץ].
Ultimately, Jerusalem’s deep corruption stemmed from her twisted approach to faith. By mixing the worship of God in the Temple with the worship of idols—believing that these false gods were His partners in running the world—she created a deeply flawed religious system. This corrupted mixture of faith is considered far worse than completely denying or abandoning the Creator [מלבי״ם].