Why do viral dances and challenges spread so fast then vanish completely

One day nobody is doing a certain dance or challenge and suddenly it seems like the entire world is participating. Then a week or two later the trend is completely gone and nobody mentions it again.

Is there a real reason why these pop culture moments explode overnight and disappear so quickly? Is it the algorithm the timing or something about human psychology that makes us jump on trends together and then drop them just as fast?