I'm assuming this happened on the UTAU wiki hosted on Fandom and not the wikidot one. Important disclaimer that I am not involved in any aspect of the UTAU wiki or editing any wiki on Fandom as a whole, so my view is just from an outside observer's.
There is a memorial on that wiki's homepage (June 5th, 2024), but I could not find ANY way to search by date on any of the wiki; both in the edit activity page and the forums baked into every Fandom wiki. Even then, I could not scroll to find the edits made around this time or any sort of page about the deletions; the tracked edit activity is only accessible for 30 DAYS. I come to find out those forums aren't even really about managing the wiki; most are just talking about UTAU and the characters themselves. I couldn't even find any link to a Discord server for administrative management! I don't think Discord should ever be the only option for checking the management on a wiki, but it's better than absolutely nothing!!
I think the reason why so many genuine UTAU's got their article's deleted is because of Fandom is entirely for-profit. With the way the website barely works, it would've been easier for all the administation to just remove all the UTAU's pages that have the trait of not being updated in ages in common instead of combing through each of the several thousand pages to determine if the character is a genuine UTAU, a troll trying to be a chuckster, or a younger person thinking they're going to make an UTAU and then giving up after a week rather than Fandom having to invest in giving their wiki's an actually decent way for the people who actually make the wiki's to moderate them. I agree that offensive UTAU's should never be made, but their information should at least be archived on a wiki (with adequite warnings about the content in the article). That's the entire damn point of a wiki! To be a genuine source for quick information and even an archive of information surrounding that wiki's topic! Instead, Fandom is so afraid of not being able to bloat every page with ads that they'll remove, refuse to host or edit anything under a PG rating.
God, I'm so frustrated with all the Vocal Synth Fandom wiki's. There are so many passionate people working on these wiki's, and it pisses me off that they have to work on Wiki's who's host fundamentally only cares about sucking money from advertisements at the cost of a functional place to get information. I desperately wish there was an alternative wiki for Vocal Synths with everything compiled and about information and culture rather than licking the executives boots, giving talented writers and editors to spread their wings.
TL;DR; Fandom sucks and I wish I had a more optimistic answer, but (until a group of people manages to get the ability to fork from Fandom and go independent, or make an entire alternate Wiki that's also hosted seperately from fandom), we're kind of screwed.
