A person lacking true wisdom is often driven not by a sincere desire to learn, but by an urge to be heard, satisfy personal cravings, or achieve quick results. The pursuit of genuine knowledge stands in sharp contrast to a superficial need for self-expression. A foolish person is defined as someone who abandons the laws of wisdom because of their personal desires, which is very different from someone who simply has doubts and asks questions [מלבי״ם]. Such an individual has no interest in deepening their understanding or expanding upon the knowledge they already possess [מצודת דוד].
The primary approach among commentators is that when a foolish person speaks, they are not looking to gain wisdom. Their only goal is self-expression, pouring out their thoughts and revealing whatever happens to be on their mind [רש״י, ביאור שטיינזלץ]. The heart is naturally hidden, but it is brought out into the open through speech. Because this type of person is driven by an automatic, internal urge to share their thoughts with everyone around them, the only thing they ultimately expose is their own foolishness [אבן עזרא, אמרי דעת].
Another perspective views this behavior as a display of pride and vanity. Even if a foolish person shows some interest in wisdom, it is merely an excuse to broadcast the little knowledge they have and show off to others [מצודת דוד, אמרי דעת]. They might display a sudden desire to learn in moments when their ignorance is exposed and they want to appear smart, but they will not invest any real effort into studying once the moment passes [רלב״ג]. Furthermore, they prefer to follow their own inclinations and desires, even when their intellect tells them that their actions are wrong [מלבי״ם].
From a different angle, this concept also applies to someone who genuinely wants to study Torah, such as a prospective convert or someone leaving a materialistic life to pursue spiritual study. Even with good intentions, a person acts foolishly when they look for shortcuts. Driven by sudden enthusiasm, they try to absorb all the information at once, completely unwilling to undergo the slow, gradual, and deep process required to achieve true understanding [אלשיך].