Where did this happen?
Well you must have looked quite a lot of episodes given Wednesday dies in the last ones.
I honestly don't know either. All I know is that Fuller and Green burst the budget for season 1, hence why they had to cut several episodes ; and then the budget they were given for season 2 was not enough for them and despite all their asks it was not rised up, so they quit.
I don't know much about the Orlando Jones drama but one thing I do know and recall happening was that when the whole affair burst out, Neil Gaiman explained that he thought Orlando was not fired, it was probably that they just did not need his character this season, due to the Lakeside arc they covered not involving Anansi in the novel ; yes I think I do recall Neil Gaiman explained that it was probably not Jones being fired as much as him not being asked to return for season 3, and the character of Anansi not being planned to appear. Neil Gaiman also added that he was sure (or hoped, I can't remember well) he would agree to return for future AG seasons.
If a twitter fight happened, it must have been about this. Neil Gaiman saying Orlando was not fired but just asked to not return for season 3 - with him planned to return in later seasons VS Orlando Jones claiming he was fired.
Now mind you, this whole business doesn't show so much the supposed "power" of Gaiman because he had little - but it actually does show the relationship Gaiman had with the actors, because we know from a lot of interviews and behind-the-scenes stuff that Gaiman took time to talk and chat with most of the main actors in season 1. Notably Orlando Jones. Orlando Jones notably wrote a character bible for Mr. Nancy that he shared with Neil Gaiman, and that Gaiman entirely approved and encouraged to put forward as the backstory of this version of Mr. Nancy. So we know Gaiman and Jones worked together to create the character (and Jones repeated he admired Gaiman's work and the man).
After that, about this dispute of claims, who is wrong who is right? We don't know. If we believe Gaiman's words, Charles Eglee did not meant wrong, just wanted season 3 to let go of Mr. Nancy for a time before returning to him later, and Orlando Jones was over-reacting. If we believe Orlando Jones, Charles Eglee refused to have Orlando Jones return because he thought Mr. Nancy as a character sent the "wrong message" to the Afro-Americans. Of course, things get complicated when you know that on one side Neil Gaiman is not aware of everything going in the show so he is not an absolute and definitive source (again, he didn't know that Iktomi in season 2 was played by a non-Native American person). And on the other side, the other Black actors of season 3 (notably Yetide Badaki and Ricky Whittle) had no particular trouble or problem with season 3's team or Charles Eglee, so it doesn't seem to actually be any kind of racism problem.
But it is true that when you look at season 3, it is painfully clear that Charles Eglee and his writing team wanted to pass a message - with the prominent character of Bilquis (plus the Orishas) sending a message of fight not through anger or violence, but through love, help, compassion, etc... When you look at the Orishas and Bilquis scenes, and have in mind what Orlando Jones said, it is pretty clear that it is highly possible Charles Eglee disliked the character and the message it sent, and thus decided to skip it for a season. On that Orlando seems to be right.
But again, the firing stuff also seem a bit exaggerated - because if I recall well, at one point there were several articles and people that mentioned how Mr. Nancy was actually planned to appear in one episode or one scene, in the very beginning of the season, but that was it, and Jones would have gotten angry at that. But I am not sure, my memory might be playing trick, it has been a long time now, so I am definitively not sure.
But yeah, this is all a muddled, complicated, entangled story that was probably taken out of proportions. (It also doesn't help that a part of the fanbase that supports Orlando Jones also showed discriminatory behavior, notably towards Ricky Whittle for not being "entirely Black" and being "half-White", so...)