I'm looking for an idiom or expression to describe a well-known person/ organization/ politician/ government whose achievements in a given situation are smaller than what they had claimed or promised to be.
We Iranians have a proverb that literally means
The (roaring) mountain just gave birth to a mouse!
Its etymology is like this:
Once a volcanic mountain started roaring, hissing, and bursting bubbles. The people were waiting to see what would happen after all those huge roarings and loud booms. Finally, the volcano activity stopped and the people saw just a tiny mouse came out of there! (rather than a monster that was expected to come). So they said mockingly:
"Heh! After all those huge roarings, the (big) mountain just gave birth to a (tiny) mouse!"
The (roaring) mountain -symbol for an apparently big(=important) and strong person-here is figured like a woman who is screaming and shouting while is delivering her baby.
We use this proverb for mocking an important person/organization/ government, etc ironically when they have used broad advertisements or have spent much money or resources over doing something noticeable, but the result/ achievement is less noticeable than it was claimed or promised to be.
Is there any equivalent for this Persian proverb?
I just found "much ado about nothing"; would it convey the same connotation?