Kind of a long story, but I'll try to sum it up.
Disco Elysium is more than a game. The world of Elysium is a project Robert Kurvitz started working on when he was a teen. He, alongside other people (Martin Luiga, Argo Tuulik, Kaspar Kalvet and possibly Jüri Saks), started Elysium as a DnD campaign, with Robert Kurvitz acting as the DM.
You may have heard about 'Sacred and Terrible Air', a novel published in 2013, written by Kurvitz. It's set in the same world as the game, Elysium. It was a commercial failure, selling only 1000 copies and driving Kurvitz to a severe case of alcoholism. I would like to make that clear because 1) It makes the character of Harry hit deeper and 2) It illustrates the potential harm taking away Kurvitz' work from him could do.
ZA/UM started off as a cultural association. It was founded in 2009, and dissolved just recently after all this shitshow (you can find the official letter from Martin Luiga, one if it's founding members, here:
). ZA/UM studio, the videogame company, was founded in 2016, I believe by the same people that founded the original cultural association, which would include at least Martin Luiga and Robert Kurvitz (I don't know about the others).
ZA/UM has basically been corrupted by it's investors, who have taken the opportunity to fire those founding members (Robert Kurvitz, lead writer and designer; Helen Hindpere, lead writer; and Art Director Aleksabder Rostov). While the reasons are unclear, I think it's safe to assume that it was due to difference in interest. The original founders probably wanted to stay true to their ideals, while the investors wanted to transform the company and the game into a parody of themselves. A money-making machine. You can see evidence of this in the deal made with Amazon to make a Prime series, in the extremely expensive clothing brand, or in the fact that they are now looking for 'Sales and Monetization Specialist' for the company:
https://zaumstudio.com/jobs/sales-and-monetization-specialist .
I should also mention that two of the main investors (I don't know if there were more), Tõnis Haavel and Kaur Kender, have charges for financial fraud and CP respectively.
So that's basically it. ZA/UM has become basically everything Disco Elysium criticized. The founders, which were basically the soul of the game, having been working on Elysium for decades, are now gone, which means that Disco Elysium's sequel (or any other game they release) will likely be a shitty bootleg copy of it's predecessor.
And worst thing in my opinion. The people who worked on that world for decades have lost the rights of their own creation. Just like that. The world they worked on for years is no longer theirs. It is one of the most unfair cases in the history of video games.
This ended up being a bit longer than I expected, but I think that's mostly it. Oh yeah. Fuck ZA/UM.
Edit: skleroos has made some corrections in a reply to this comment. Be sure to read it as he seems much more knowledgeable about the details than me.