Samuel's message deeply moved the Israelites, prompting them to purify the land from idol worship [ביאור שטיינזלץ]. Their complete return to God is shown entirely through concrete actions, unfolding in two distinct stages. First, they repented for their past wrongs by physically removing the idols. Then, they established a firm commitment for the future by choosing to serve God alone.
The narrative focuses strictly on the physical actions the people took rather than exploring their inner thoughts or intentions. This is because only God truly knows the hidden secrets of the heart [מלבי״ם].