No one plans to go crazy.
And after you go crazy, nonsense becomes reasonable.
If Kes wasn't suffering from dementia, if she was still sane, and still acted like that, then that would be out of character, but insanity changes your character.
Okay here's a question.
If Kes was kookoo for cocoa puffs, why did they put her behind the controls of a Starship and push her off into space?
That's right up there with friends don't let friends drink and drive.
Would you really let you grammy who keeps putting gold fish in the tea kettle drive her car to the shiops for groceries?
Sounds like a mercy killing to me.