>>44641511SM is based in the ying yang concept, just as BW was. So the game always plays with the black and white, the sun and the moon.
The region looks like a paradise, is charm, happy, full of nature... But also cruel, dark and shows you the dark side of nature. This also happens with characters and how everything in the region is grey and has a sun side and moon side, for example Team Skull not being just bad people and being actually a family, or the organization that protect the Pokémon in the region, Aether, having corruption inside. Even Guzma has a reason why he does what he does, and Lusamine same with her husband... That’s the concept SM plays with all the time.
And that’s why the region or rotom looks happy but has the darkest entries in the franchise.