The spiritual decline of Jerusalem reaches such a profound low that it creates an absurd reality. Cities historically famous for their wickedness suddenly appear innocent and pure by comparison. Samaria, a neighboring kingdom known for its corruption, did not commit even half of the wrongs that Jerusalem did.
The vast gap between the two kingdoms stems from several factors. While Samaria failed primarily in matters of idolatry and duties toward God, Jerusalem added severe crimes against fellow humans, such as murder, oppression, and robbery. Furthermore, Jerusalem enjoyed an extraordinary level of spiritual closeness. The city was home to the Temple, the Divine Presence, the high court, and numerous prophets who constantly guided and warned the people. This intense spiritual privilege makes her betrayal far more outrageous [מלבי״ם]. Adding to this downfall, Jerusalem actively absorbed corrupt cultures from all the surrounding nations, drawing in foreign influences from Assyria, Babylon, Egypt, and Canaan [ביאור שטיינזלץ].
By multiplying her terrible acts far beyond Samaria and her surrounding towns [מצודת דוד, רד״ק], a shocking outcome emerges: Jerusalem effectively justifies her sister cities. The primary approach among commentators is that Jerusalem did not actually turn her neighboring cities into righteous places. Instead, against the dark backdrop of Jerusalem's endless offenses, the historical crimes of Sodom and Samaria are dwarfed. To anyone watching, their past actions suddenly look like acts of righteousness [מצודת דוד, רד״ק, אברבנאל].
From a spiritual and legal standpoint, Jerusalem essentially hands these notoriously wicked cities a valid defense claim before God. They can now point to Jerusalem and argue that someone else angered Him far more than they ever did [רש״י]. Although the immediate comparison focuses on the single sister kingdom of Samaria, the ultimate judgment expands to include Sodom as well, grouping both cities together in the shadow of Jerusalem's unprecedented failures [רד״ק].