Hahahah yes, those crabs are like seafood action heroes. Silvester Crabone and Jean Claude Van Crab.
That behavior is probably connected with reproduction. It could be two males fighting over territory. Or maybe even a misunderstanding between a male and female that didn't turn into mating. I don't know enough about this species to be sure what it is.
Wow! That's interesting... never knew craps fight over territory too