Let down.
Let down.
To "let down" means to disappoint someone, typically by failing to meet their expectations. Imagine holding a balloon filled with someone's hopes, and suddenly the air escapes; that deflation is akin to the feeling of being let down. This idiom reflects the sadness or betrayal one might feel when someone doesn't fulfill their promises or duties.
She felt let down when her friend didn’t show up.
She felt disappointed because her friend didn't show up when she expected.
He let down his teammates by missing the meeting.
He disappointed his teammates by missing an important meeting.
When the product failed to work, it really let down all the customers who had high expectations.
The product failing to work was disappointing for the customers who had high expectations.