basically the summary of the situation is that kemono friends was expected to fail and fail hard, so kadokawa gave the director and his team full creative rights over the show. but since it ended up being super popular, kadokawa wants them back and the director told them to go fuck themselves because they gave absolutely no support in making it a success. so they fired him.
the official line is that Tatsuki's been fired because the director's team made a short little bonus episode (12.1) just for fun and gave it out for free, which pissed kadokawa off because they could've sold it as a bd bonus.
so, just usual evil corporate bullshit.