A nation's descent into idolatry often reveals itself through an obsession with building monuments. Ephraim sank deeply into this spiritual corruption, constructing countless altars dedicated to calves and foreign idols [רד"ק]. Originally, an altar was intended to serve as a place of atonement and connection to God. However, these structures achieved the exact opposite, becoming a source of guilt simply by existing [ביאור שטיינזלץ].
The relentless multiplication of these altars points to several layers of spiritual decay. One perspective highlights a generational compounding of wrongdoing. Ephraim inherited a legacy of idolatry from previous generations, yet rather than abandoning these practices, the people actively expanded upon them, building even more altars just as King Ahab had done [אבן עזרא, רד"ק].
This deep-seated commitment to idolatry can also be understood as a progression from thought to action. The initial desire to build altars reflects the deliberate intention to sin, while the subsequent reality is the physical act of offering sacrifices without any regret [מצודת דוד]. Furthermore, in the realm of idolatry, a mere intention is judged with the same severity as a completed act. Therefore, the very planning of these structures was counted against Ephraim as if the physical altars were already standing [חומת אנך].
The destructive nature of these altars extended both outward and inward. The people not only used these sites to lead others astray, but the altars ultimately became a personal trap and stumbling block for those who built them [רד"ק בשם תרגום יונתן].
On a deeper psychological and political level, this obsession with building altars stemmed from a desire to assimilate and forge alliances with foreign nations. This resulted in a profound moral confusion where the people completely lost the ability to distinguish between right and wrong. In their distorted view, the countless new monuments they built for idols were not sinful at all. Instead, they twisted reality to such an extent that they viewed their original, ancient altars dedicated to God as the true source of sin [מלבי"ם].
Ultimately, this absolute devotion to idolatry and the endless multiplication of altars sealed the nation's fate. As a direct consequence of their actions, Ephraim was destined to suffer the heavy and oppressive burden of foreign rule [רש"י].