A miraculous display of heavenly fire descending in full view of the people completely shatters their previous understanding of the world. This profound moment leads them to an absolute recognition of the singular nature of God. Witnessing this wonder, the immediate reaction of the people is to fall to the ground. This physical surrender stems from a place of deep awe [ביאור שטיינזלץ], serving as an act of complete submission to God [מצודת דוד].
Immediately after, the people cry out in recognition of the absolute truth [ביאור שטיינזלץ]. Their declaration is a clear statement that God alone is the true deity, while the idol Baal holds no power at all [רש"י]. On a deeper level, this outcry uproots the common idolatrous belief of the time. Idol worshippers believed in two separate ruling powers, one responsible for good and another for evil, assuming that opposing forces could not come from a single source. However, as the people watch the heavenly fire consume the water in the trench without being extinguished, they see with their own eyes how two opposites can exist together. This realization leads them to understand that the divine attribute of mercy and the divine attribute of judgment are not two separate domains, but rather one single essence [אדרת אליהו].
The people repeat their declaration of faith twice. The primary approach among commentators is that this repetition serves to strengthen and emphasize the new belief that has just taken root in their hearts [מצודת דוד, רד"ק]. Another perspective views this repetition as two distinct conclusions drawn from the event. The first statement is a positive affirmation that God is the true deity, a truth learned directly from watching the fire descend from the sky. The second statement acts as a rejection of any other power, emphasizing that there is no one but Him, a realization born from the understanding that the idols of Baal are a complete lie [מלבי"ם].