Riding a trend or a craze can be profitable if you get it right.
As a general rule, trends last a reasonable amount of time whereas crazes are often forgotten almost as soon as they happen.
Sometimes there’s a crossover – the song Macarena was popular for a lot longer than a normal song but you knew deep down that it was only a craze when seemingly every politician felt the need to show they could act out the movements.
If Teespring had been around you’d have made a lot of money selling T-shirts with pictures of people making a fool of themselves.