It’s the idea of a New Sincerity, or post-postmodernism.
Yeah, the world is turning to shit, and nothing matters. So what? What are you doing to make it less shit?
It’s the idea that you should be trying to save everyone with the understanding that a small portion are just too far gone to be saved, and you should focus on the ones that you can, because even if you just save one person, that’s still a net positive.
Nobody said it had to be a solid sphere, how else would you get it to emit the ominous hum without attuning its natural frequency by carefully designing the thickness of the obsidian layer?