The little Dutch girl was orphaned in World War II. She may be Happily Adopted, but that doesn't negate the tragedy.
Kris has been tricked into the taxi going to Bellevue by Sawyer. He asks if Doris knows about this. Sawyer says that "yes, we all discussed it." Kris stops struggling, obviously depressed. It takes hours for Fred to show up, so that was hours that Kris sat all alone thinking that Doris had betrayed him after humoring him like any other old man.
Fred: She didn't want to hurt you. Kris: Only because I was a nice, kind old man she felt sorry for. Fred: That's not true. Kris: Yes, it is. She had doubts. That's why she was just sorry. If you'd been dragged off here, instead of me, she wouldn't have been sorry. She'd have been furious. Fred: All right, she had doubts. Why not? She hasn't really believed in anything for years. You can't expect her to suddenly... Kris: Oh, it's not just Doris. There's Mr. Sawyer. He's contemptible, dishonest, selfish, deceitful, vicious... yet he's out there and I'm in here. He's called normal and I'm not. Well, if that's normal, I don't want it. That's why I answered incorrectly.
In the book adaptation, Kris doesn't deliberately fail his mental exam at Bellevue: he's so heartbroken that he simply loses his will to fight, and barely makes any effort to answer the questions, mumbling whatever comes to mind in a lifeless voice.
1994 Film
This version has Kris arrested and the scene of him sitting alone in his room at the mental ward, sighing in shame, just breaks your heart.
The orderly walking by and seeing this looks like he's about to burst into tears.
