A moment of profound clarity often follows a long period of self-deception. The people offer a sincere and deep confession, fully recognizing their past mistakes and waking up from the false sources of salvation they once relied upon. They openly admit that they truly [רש״י] and pointlessly placed their hopes in foreign, useless forces.
For a long time, the people looked to the hills and mountains for help, but they now confess this was nothing more than an illusion. The primary approach among commentators is that this misguided hope refers to idol worship. The people realize that expecting salvation from the idols perched on the hills, or from the noisy rituals taking place on the high mountains, was a complete lie [רש״י, מצודת דוד, רד״ק, ביאור שטיינזלץ]. The sheer abundance they describe [מצודת ציון] might point to the vast number of idols themselves [מצודת דוד], or it could represent the massive, loud gatherings of worshippers crowding the peaks [רד״ק, ביאור שטיינזלץ]. Painting a vivid picture of this scene, some explain that the lower hills surround the taller mountains, creating a space where the loud chants of the crowds on the mountain bounce and echo off the surrounding hills [מלבי״ם].
Alternatively, rather than a literal scene of idol worship, this confession can be understood as a political allegory. In this view, the hills and mountains symbolize the various nations of the world. The people express deep regret for looking outward for military support, realizing how foolish it was to hope that a multitude of foreign nations would rush to their rescue in times of trouble [רד״ק].
Having shattered the illusion of relying on these heights, whether they represent false gods or foreign armies, the people arrive at a clear and absolute truth. True salvation comes exclusively through the help of God [מצודת דוד]. Unlike the unreliable nations of the world, God actively watches over Israel for their benefit, always protecting them as long as they walk in His ways [רד״ק]. This profound realization leads to a firm and final decision to follow only Him from this point forward [ביאור שטיינזלץ].