I think there was a rumor that she was replaced at one point, but the voice actress swears that it never happened. Hard to tell, all things considered. Her identity was a mystery for a long time, but eventually actress Nozomi Kasuga was identified as the voice
Doesn't matter. That should have been the end of it. The fact that they replaced her and didn't tell anybody damaged their reputation in some peoples eyes. Her leaving for nfts just cut the wound deeper
Im almost certain its not the same person
Here's the thing. They technically did and didn't.
Upd8 realized early on that Kizuna Ai growing too big meant she would be stretched too thin between doing Youtube content and doing celebrity things (concerts, interviews, TV etc), so they hired extra VAs to keep up with the growing demands of Kizuna Ai. They never outright replaced Ai, more like placed a substitute while the OG Ai is busy with concerts and whatever.
The problem here is that the either the management or Nozomi Kasuga decided never to tell the fans that they would be hiring extra VAs to keep up with the projects and that they placed the substitute on Youtube, the place were most of her fans know and love her. So while OG Ai is still definitely active (albeit not on Youtube); fans were quick to realize that the one handling the Youtube channel was definitely not the OG Ai.
And by the time Upd8 came forward and said, yes, we hired extra VAs and the launching of the multiple Ai projects, it was already too late. Fans already felt discouraged because the company thought they could just "replace" Ai with nobody noticing.
TL;DR: Nozomi Kasuga was still active as Kizuna Ai, but they did hire replacements to stand in for her.
It's easy for a creator to feel that they're "small" at 17k, until you remember the unbridled mass of wannabe nobody streamers and YouTubers who make content under 5 people will ever watch. There are so many people wanting to make it in this industry that by the time you're pulling the numbers even Pippa has, you're probably in the top 1%.
If you're learning to draw/play guitar/anything, how do you improve if all you're doing is going "Yeah, I suck, but at least I'm not at the level of literal babies". No you don't, because that means you're complacent and no longer interested in improving. You should always find ways to improve, and ask yourself what you you could do better to be at the same level as others.
Pippa/Yuni knows she already "made it" as a Vtuber, but she also knows she's clearly lacking in something because her peers have already beat her despite her early lead.
Being disappointed in oneself is the crossroads Pippa/Yuni needs to overcome if she really does want to be bigger as a Vtuber/content creator. The first step in improving yourself is identifying what it is to improve on.
I just hope this doesn't discourage her, rather I hope this inspires her to be better