Why does the promised youth fail to live up to their potential?

It's not for lack of talent, but for lack of understanding.

Talents, like everything else, need to be managed, otherwise they can be as more liability than asset.

---Ecclesiastes/Kohelet 9:11-18

I have further observed under the sun that The race is not won by the swift, Nor the battle by the valiant; Nor is bread won by the wise, Nor wealth by the intelligent, Nor favor by the learned. For the time of mischance comes to all.

And a man cannot even know his time. As fishes are enmeshed in a fatal net, and as birds are trapped in a snare, so men are caught at the time of calamity, when it comes upon them without warning.

This thing too I observed under the sun about wisdom, and it affected me profoundly.

There was a little city, with few men in it; and to it came a great king, who invested it and built mighty siege works against it.

Present in the city was a poor wise man who might have saved it with his wisdom, but nobody thought of that poor man.

So I observed: Wisdom is better than valor; but A poor man’s wisdom is scorned, And his words are not heeded.

Words spoken softly by wise men are heeded sooner than those shouted by a lord in folly.

Wisdom is more valuable than weapons of war, but a single error destroys much of value.