מלכים ב, פרק י״ז, פסוק י׳

The spread of foreign worship across the land marks a severe and advanced stage in the people's rebellion. By setting up stone pillars and designating trees specifically for worship [ביאור שטיינזלץ], they showed a sharp escalation in their wrongdoing. At this point, they transitioned into complete idol worship, fully imitating the practices of the surrounding nations. They committed these evil acts with the deliberate intention of angering God [מלבי״ם].

The physical arrangement of these rituals was specific, as the stone pillars were purposefully placed down in the shade of leafy trees [מצודת דוד].