Why does the bowed fiddler crab have such a gigantic pincer?

The fiddler crab has a pair of chelae of different sizes. The major chela looks like a violin, while the minor one always rubs against the major. It seems to be playing the violin, but in fact, it is clearing the mud or other things from the major chela. #AnimalAdventure For more: https://english.cctv.com/ | CCTV

#Beachcombing - Fiddler Crab

European Fiddler Crabs | National Geographic