...assuming that they knew they were looted. You could make a case that, yes of course these items were looted, and they turned a blind eye to that. But you could also make a case that they trusted a 3rd party to validate the artifacts.

Don't forget this is the group that voluntarily funded research that eventually proved some of their most prized possessions were, in fact, forgeries[0], so we have to assume they have at least a modicum of ethics.

[0] https://www.nationalgeographic.com/history/2020/03/museum-of...