I wouldn't expect that the "general looter" would loot the Museum. It doesn't make any sense, unless the Museum was not open to the public and people in general were not aware of it's significant. It is possible (or even likely) that the Museum was not available for the general public. The Museum could have restricted in a number of different ways:
The Museum could have been reserved for "tourists" and be a sort of Govt PR. It could be open only to a selected elite. Or it could have simply had a high admission price and thereby limited access.
So if the Museum was alien to the public then I can see why "general looters" would trash the place.
But even regardless of if the Museum was open to public, it's possible that the Museum was looted by a "selected group". This group could include the upper class, Museum personnel, "special forces" from other countries, or even a group which have been "somehow" been badly treated by the Museum.
Now, I think this looting should throughly investigated- and the first suspects would be the people who were "dismayed" over the looting.