flash in the pan
something that happened only once or for a short time and was not repeated:
Sadly, their success was just a flash in the pan.

[TahlilGaran] Advanced Learner's Dictionary ▲

flash in the pan
briefly successful or popular.
At first, some of the major record labels thought rock ’n’ roll was just a flash in the pan.

Usage notes: sometimes used in the form no flash in the pan - successful or popular for more than a brief period:
This trend is no flash in the pan.

[TahlilGaran] English Idioms Dictionary ▲

flash in the pan
someone or something that makes a flashy start and then fails
The man's sports career was a flash in the pan. Recently I have not heard of him at all.

[TahlilGaran] English Idioms Dictionary ▲

flash in the pan
n. phr., slang A person or thing that starts out well but does not continue.
The new quarterback was a flash in the pan.
Mary got 100 on the first test in arithmetic but it was just a flash in the pan because she failed in arithmetic.

[TahlilGaran] English Idioms Dictionary ▲