I remember that The Pokémon Company claims on its website that all fanart is its property (with the artist surrendering it and stopping any further pieces featuring its properties.) Granted, the company isn't that strict with enforcing it outside of major cases due to practicality reasons. Disney probably takes a similar stance where it believes that fanart is fair game because it features its characters. It's scummy but unsurprising.

Uh something something Disney porn vault…