How much of this vandalism is is iconoclasm for religious purposes and how much of it is to cover theft? I think that selling black market antiquities would be a great way to raise funds, and if the site is thought to have been totally obliterated, no one is going to try to track down the smaller pieces.
You just answered my main questions on why were they not selling these articles for the money. They most like are selling the most valuable, but yes, if we are told that entire sites have been ‘destroyed’, no one will be looking for them as they pass from sheikh to sheikh.