> 5 Use case: cave exploration as an artistic manifestation

I guess that's their answer, where calling it art is kind of a sophisticated way of saying "because it's cool". Also, the cave in question is close to them and somewhat recently discovered.

Since even a moderate breeze would make this uncontrollable in open atmosphere, it seems like a cave is one of the only places this airship can be used. And even then many caves have strong drafts that could totally disrupt use.