Everyone thought the block was on HoloEN side for a while since Myth was quite isolationist during their first year.
But once Myth started doing vshojo, indie and 3DPD collabs(TT), people started to notice that they were avoiding NijiEN, despite Pomu and Kiara being on good terms.
I'm gonna try and build up some form of a timeline for the Holo-Niji related stuff that's relevant to this collab block. Mainly with respect to Pomu and Kiara, since those two are the only Holo-Niji EN combo who have expressed interest in a collab.
1. Ollie collabs with Gundou from NijiJP on 28th July 2021 (
https://youtu.be/Ghzt6N1WB14). This was around 2 months after NijiEN debuted.
2. One day before this collab, Pomu and Kiara had their first of many on-stream (chat only) interactions (
https://youtu.be/ZRb4HsiQXc8?t=6497).
3. 3 months later, in October 2021, Kiara reported that her collab request for Pomu had been rejected :
https://youtu.be/eMQF7VPADI8She didn't specify who did the rejecting. Considering that she had been quite candid about shitting on HoloEN management at the time, but avoided blaming any party in this instance, it was pretty obvious to guess that the block came from NijiEN side.
4. About a month later (late November), it was revealed that Lazulight was attending a singing event held by Bilibili, so this may have had something to do with it :
https://old.reddit.com/r/Nijisanji/comments/r3koxh/half_of_2434_international_will_be_attending_sing/5. Around the same time of the above reveal, Selen said that she finally was allowed to collab with Ollie but that was postponed and then cancelled, with nothing else coming of it (
https://youtu.be/qH_lYfNNw78). Speculation is that Selen's manager got permission from Cover's side for the collab and so Selen thought it was fine to announce it on stream (since once Cover's side was clear, obviously she assumed NijiEN would be fine with it). But the Lazulight Bilibili announcement may have caused NijiEN higher ups to veto it so that Lazulight could still attend the event.
6. December-January : Luxiem debuts and gains a humongous audience from China, inclining the entire branch and becoming the most successful NijiEN wave to date.
> Pomu - Kiara interactions - both on-stream(YT chat) and off-stream(twitter) - are still happening in the middle of all this btw.7. March 5, 2022 : NijiEN discord leak. Irreparable damage to NijiEN perception in the eyes of hololive fans - specifically Fulgur. Damage is far more to NijiEN fans' reputations thanks to their reaction, but the livers' behavior was also frowned upon since they were outwardly friendly towards Holo. Pomu didn't have any major involvement, so her reputation is still relatively clear.
8. May 1, 2022 : Luxiem officially get Bilibili channels (
https://twitter.com/nijisanji_world/status/1520712132718964736).
9. July 13, 2022 : Pomu Birthday stream, when starting to read pre-recorded messages, reveals that there was "one more" but asks her fans to pretend that she read it on stream. Highly likely that this was Kiara's birthday message, but Pomu explicitly avoids confirming it despite freely being able to namedrop Kiara in prior streams (
https://youtu.be/zkAecWb_yTs?t=10401).
10. July 21, 2022 : Kiara SC reading stream, SC references Pomu collab. Kiara reveals that she had been hopeful for a while, but looking at "recent developments", it felt like it was never gonna happen (
https://youtu.be/qEPw2vxjTaw?t=15873).
11. Aug 06, 2022 : Pomu sends the contents of her bag for Kiara's bag reveal stream (
https://youtu.be/wtRj5RGlMHA?t=6371). Indicating that Hololive management has no problem with Kiara involving Pomu in her streams.
12. Pic related is the latest clue we have, where the post discussing the aforementioned incident was deleted from the Nijisanji subreddit with no explanation, but was not deleted from the Hololive subreddit, which explicitly has a Rule against "advertising VTubers outside of Hololive". Even the Hololive mods commented on that post, telling people to chill, but did not lock the thread, delete the post or prevent discussion.
At this point only Nijiniggers think the block is on Hololive side, and they have to willingly ignore every piece of evidence that points to the block being from NijiEN side. Very likely due to a large part of their audience now being from China.