[Gumption]

Even without considering monetary value involved the propaganda value of the robbery would be immense. Then think about the havoc it would reap on the local economy with all that extra money floating around.

[Burkeman1]

Perhaps it was a mixture of both? Greed and Fedeyeen. Attack a convoy loaded with money. Maybe even get lucky and score a few bags of greenbacks (or whatever color Dinars are) that don't get burned up or destroyed during the assualt?