Specifics depend on which rrats you want to believe, but it all kind of came down to Elia being a bad influence... Causing drama with Mozzu over male collabs (supposedly she got one of the other V-Dere girls to join her for a male collab and then ditched her), Twitch whore pandering, etc. I remember around the time of the Japan trip when people (even some people here) were talking about V-Dere possibly disbanding, /vt/ was arguing back and forth over whether Mozzu or Elia was the one causing the problems. Considering Mozzu is still there and Elia is now an indie I'd wager we have our answer. Funnily enough, Mozzu antis moved on to other shit after the drama stopped instead of admitting Elia was likely the problem... last I saw, I kid you not, Mozzu haters were complaining that she hadn't banned/blocked you specifically Proctor.
It's also been heavily theorized by anons that the "great opportunity that fell through" which Ekko once mentioned played a part in her departure from EIEN (should be here:
https://thevirtualasylum.com/threads/eien-project-disintegrates.265/post-531582 but Ghost Archive isn't working for me right now) was her friend Elia getting her into V-Dere - which combines very nicely with the rrat that each gen 1 V-Dere member got to pick one person for gen 2. It also tracks as Ekko follows all of the V-Dere girls on Twitter except Mozzu, as if there's some beef there, but of course rrating off of Twitter follows is exceptionally schizo. My personal rrat was that Elia was the friend pre-debut Ekko mentioned was trying to convince her to move to Twitch... I'd dropped it for a while because someone pointed out that Elia was a YouTube streamer but now seeing this rebrand and seeing Elia's Twitch linked on her Twitter instead of her YouTube, I'm somewhat inclined to start believing it again.
There's probably more and some reason that Elia is commonly referred to as the "whorse," but I never followed Project Kawai or V-Dere and only started paying attention from the perspective of an Ekko fan. As to why anons were right to worry, seeing this redesign gives me serious doubts that Elia is someone who should be trusted for advice. Ekko for example has mentioned she already has a 2.0 and 3D in the works and I shudder to think that she might ask Elia for feedback and value her opinion because holy shit I do not want the person responsible for this abomination of a redesign to start influencing other people.
Edit: just to note, I don't know the first thing about Elia outside of reading about her here and on /vt/ and seeing her in collabs with Ekko... I'm not trying to be an Elia anti and if she's actually a good friend to the V-Dere girls/Ekko/others then great - but seeing this 2.0 and the apparent Twitch pivot I do not trust anything she could say regarding models/content direction/etc would align with my personal VTuber preferences in any way.