I don't know anything for sure of course, but I think Marvel may have a bit less to worry about in terms of something like this being potentially detrimental to their brand, or otherwise playing a big role in framing how consumers view their product. Marvel has so much crap out there, and they're going to be making money with merchandising hand over fist anyway, that a bootleg 1/6 scale figure or set here or there doesn't really matter much. But with 2000AD, they don't have much merchandise, and might be a bit more restrictive and possessive of what is done with their characters and other intellectual property. Plus, even if it's a nice piece (which this seems to be), allowing this would set a precedent that others could try to milk Dredd stuff with impunity. Then of course, there is the fact that they aren't being given proper credit and payment for the use of their property, which I would assume is also playing some role.