It’s not every day you hop on a bus, accidentally go through a door in space, and end up on a desert planet with nothing but sand as far as the eye can see. All things considered, the Doctor decides the passengers are handling the situation pretty well.
It’s hot; deserts are like that. Being inside a metal bus in a desert isn’t ideal, but it’s better than the alternative. Outside, they’d probably roast. Everyone is scared and worried, but they needn’t be. After all, they’re lucky. They’re with the Doctor, and one way or another, he’ll get them home.