I'm not privy to the reasons behind her graduation. There have been multiple rrats from disputes with other talents, problems with management, desire to own the rights to her music, etc but as for what actually happened I have no clue. I do know that she was unaware the company was closing before her graduation, and that she was never offered her model/IP (though she did inquire about purchasing it on at least one occasion after the closure announcement was made).
As to her complete disappearance, I again am just as in the dark as you are. She had the trip to Japan with V-Dere planned for late October, so not redebuting before then makes sense. She's claimed she had what she thought was an amazing opportunity that fell through that some people believe means she was offered a spot in the new V-Dere gen before Elia left (coinciding with the rrat that each V-Dere girl got to pick one newcomer, and she would have been Elia's), but she's also claimed she originally wanted to debut in November but the model/rigging wasn't ready. She's stated she tried to leave "hints" for people to find her new account (which, to be fair, did work as I was following the Ekkomori account before Kilia had even graduated), but overall I agree with you - she definitely did not capitalize on any momentum. Kilia had (in my biased opinion) a world class model, so waiting all the way until February to debut with a model that doesn't measure up to Nemo's (formerly Nanimo Navi of EIEN, so started the rebranding process later) is definitely bizarre. A cynical person would say she felt pressured to debut before Valentine's Day, for obvious reasons, even though she's unhappy with her current model (she already claims to be working on a 2.0 using Kilia's mother).
Ultimately I agree with your assessment of the move to Twitch. For sure if you're in her Discord there are people who shill the hell out of Twitch, for reasons that are entirely unknown to me. But changing streaming platforms is essentially a death sentence for the average fan that's relatively uninvolved and just watches streams (literally me before I found her as Kilia). I can only guess that the people pushing for the switch are misguided fans who think the only route to success as an indie is to follow in the footsteps of the /lig/gers, or are bad actors trying to take advantage of the chaos to become certified groomers as her audience shrinks and, as
@frz pointed out, she moves to a more interactive platform that is more conducive to "hoe-fication." I would like to believe the first scenario is significantly more likely, but now that I've seen her not give any indication of the ability to process the possibility of having bad mods I am more wary of her ability to weed out the problematic people in her community.