I can only think of a few reasons someone would do this, in descending order of probability
1) money. They have a buyer or buyers on the black market. This seems like the most likely option.
2)private collection - though it would be hard to sit on something like this without showing and telling...
I know this is a dated article (2018), but it makes me wonder how often robberies, heists and forgeries occur in the collectible hero prop world. Anyone have any insights? Occasional opportunists or a bigger brewing problem...