The developers of Fedi software have different philosophies. Some developers are just not interested in implementing and supporting all kinds of AP actors, kinds of media, ways of attaching media etc. Because they want their software to focus on a certain thing.
Others want to implement everything and interconnect with every platform.
Afaik he tolerated no support for calls for violence whatsoever on his instance. Which is his freedom to do as his line of moderating, but obviously brought him into conflict with the beliefs of many on Lemmy