Why should you not overuse "knew"?

Why should you not overuse "knew"?

Try to eliminate overusing the word knew. Rather than tell us what you or your main characters knows, show it through their actions.

Original: Lisette knew her mother was furious.

Rewrite: Lisette's mother slammed her hand down on the kitchen counter and pushed all of the dishes off the edge. Her voice clipped and hard, she said "Stop."