What does this idiom mean?

Metaphor is that talents are not reused. This is not an idiom.

Synonymous idioms

to cast pearls before swine

Basic explanation

The original intention is bright pearls, which are secretly thrown on the road, which makes people surprise. Metaphorically speaking, talented people are not valued. It is also a metaphor that good things fall into the hands of people who don't know the goods.