Obsession is a form of madness. When obsession becomes the only thing in someone’s life, that person becomes at least temporarily insane.
When a fiction writer creates a portrait of a person whose quest or search for something or someone or some ideal becomes all-encompassing…they are creating a character who, as they inhabit the story at least, is for all intents and purposes…unhinged.
A writer should love something about every character they envision and inhabit, but to fully realize a character and to avoid sentimentality or what I can only call “falseness,” the writer has to recognize that insanity. If the writer doesn’t–can’t pull back enough to recognize it, no matter how close-in and personal the writer gets within the story–then you get the odd situation in which the writer clearly thinks they’re writing a story about a genuinely good, genuinely sane person when they’re not.
Just an interesting thing to observe, because although there are some subjective elements about characters and ambiguity, you can also say that if a character does certain things in certain contexts, most reasonable people would feel a certain way about that character after awhile.