A sharp agricultural image captures the tragic spiritual decline of the nation. There is a painful irony in how the people responded to the immense wealth God gave them. Instead of showing gratitude, they used their God-given abundance to deepen their betrayal and sin.
The nation is compared to a dry, empty vine that has lost its strength to produce anything of value [רד״ק, אבן עזרא, מצודת ציון]. Spiritually, this is a vine that drops its good fruit because the people have abandoned God [רש״י]. They have emptied themselves of spiritual wisdom and the fear of heaven [מצודת דוד]. Rather than yielding the expected harvest of justice and righteousness, the nation has become entirely hollow and rotten [מלבי״ם, ביאור שטיינזלץ].
When considering the fruit this vine might desire or produce, several perspectives emerge. One approach views their situation as a delusion born of pride: even though they are like a dried-out vine, the people still imagine they can generate a worthy and abundant harvest [אבן עזרא, ביאור שטיינזלץ]. Another perspective raises a doubtful question: does a nation so depleted, having been plundered by its enemies, even deserve for God to grant it any success at all? [מצודת דוד, רד״ק]. Alternatively, the lack of fruit is seen as the direct result of their sins. The bitter harvest of their evil actions is exactly what caused their emptiness, bringing disaster upon themselves through the false altars they built [רש״י]. Looking toward the future, this fruit also represents the next generation; the children born to the nation will be just as corrupt and empty as the vine that brought them into the world [אברבנאל].
The root of their ingratitude is seen in how they handled their prosperity. As God showered them with goodness, increasing their wealth and blessing them with children, they took this very abundance and used it to multiply their altars for idol worship [רש״י, רד״ק]. Rather than raising their growing families to serve God, they taught their children to worship false gods [אברבנאל]. This tragic pattern continued with the wealth of the land itself. As the soil produced better harvests of grain, wine, and oil, the people did not thank God. Instead, they took their riches and invested them in erecting and decorating pillars, which were altars carved from a single stone [מצודת ציון]. They used their agricultural success to build beautiful monuments dedicated to idol worship and national pride [רד״ק, מצודת דוד, מלבי״ם, אברבנאל].