This is petty fandom salt, BUT... I've been chewing on this phenomenon that I've been calling "Fandom's Darling". It is related to things like "Author's Darling" and "Mary Sue / Gary Stu" and "Protagonist Halo" and all that jazz, where one character gains a peculiar narrative weight in a story.
"Author's Darling" is when a writer has a favorite character, and the world and all other characters sort of get... warped to put the Darling in the spotlight. It's most noticeable in TV shows with multiple writers, when a character you personally like suddenly has their previous characterization destroyed to make another character look good somehow. Every other character might become weirdly incompetent. The Darling's feelings are treated as The Most Important Feelings in any given situation. The logic of the fictional world seems broken past suspension of disbelief in order to validate this one character's beliefs or skillset or some other fantasy. And so on.
"Fandom's Darling" is what I've been calling the pattern where a fandom essentially crowns a New Protagonist for their fanfiction stories (often a side character rather than the original protagonist, but it can also happen to protagonists). This character becomes the self-insert for all sorts of indulgent power fantasies, gaining special powers or backstories, and/or becoming the focus of whump, and/or hooking up with various hotties, starring in all sorts of tropey AUs, and so on. They're not always an obvious Mary Sue version of themselves, but the character's original personality and interpersonal relationships tend to get warped or dropped completely. I call it "Fandom's Darling" because it's not just one self-indulgent fantasy fic (you do you! Have fun!) with characterization that I personally don't like (I have neither the time nor the desire to police anything, I am just venting), but rather a mini-fandom of sorts revolving around this empty doll / fanon version of the chosen vessel character.
I am salty about this (mildly frustrated) (imagine a soft sigh of disappointment before I go do something else) because you are FUCKED if you actually liked the canonical version of this character and their interpersonal relationships. It's almost worse than liking an obscure character that no one cares about. There's about a thousand fics starring your fave, but maybe only about a dozen of them are actually rooted in any kind of recognisable canon.