Michelangelo was just starting out and needed money. In those days the market was for antique (old Roman or Greek) statues, not modern ones by unknown artists.
So he carved a statue of a Cupid, “aged it”, i.e. made it look old, and then palmed it off on a cardinal as an antique work. A merchant did the dirty work of selling it for him.
In time, the cardinal got wind of the fraud and made the merchant give him his money back. He then returned the Cupid to him in disgust.
Michelangelo’s biographer-buddies had the cheek to blame the Cardinal for returning the statue after he had discovered it wasn’t ancient. “A guy with all his money could have kept the Cupid anyway,” they said. “Everyone agreed it was a very beautiful work. This shows the Cardinal didn’t know a good thing when he saw it.”