It was used because of the nature of blockchain transactions as operations, but everything is simulated so no cryptocurrency is involved. Instead, every transaction represents a possible state change in the murder mystery (e.g. Alice walks from the Kitchen to the Bathroom). If the state change breaks any rule (e.g. let's say no more than two characters in the same room), then the transaction reverts and the fuzzing tool keeps exploring.

Edit: I guess an expanded version of this should be in the README