Quite possibly, in that it is 'easier' (after all the risk entailed in the salvage of the wreck, ofc) to sell plain gold in some form rather than historical artifacts that are easier to track, more notable, have a smaller audience, etc etc. Its tragic, but sensible in a cold blooded, economical fashion.

E.g. Would the criminal enterprise that went to such great lengths to obtain the material rather sell a sizable quantity of unmarked gold ingots to WeDon'tCareWhereItCameFromJewelers LLC for a nice return, or go through an arduous process to sell coins in varied quantities to wealthy collectors.