Because lots of trans people are into programming (disproportionate compared to the average) and like memes around that specifically, and want a community specific to viewing discussion and memes around those specific topics in combination. Furthermore, it means that sort of content won’t be lost or removed like it might on general purpose communities. And it provides a nice way to meet other trans people with similar hobbies.

Also, lots of programming communities have a history of being very comfortable hosting transphobia and having specific trans friendly zones is often useful so you don’t have to constantly mentally ready yourself to see casual bigotry accepted >.<

Even with a somewhat more leftie culture on lemmy, having trans specific spaces means trans people can go there without feeling the expectation to constantly rehash “gender 101” to the more uninformed parts of the general population when they ask insensitive questions (seriously, I’ve had people ask me about my genitals to my face more than once, they were well meaning and I explained but… yeah), which is exhausting to constantly do even ignoring the decent chance it’s actually a bad faith actor trying to spread bigotry or bioessentialism or general antagonism to trans people via sealioning.

I also don’t understand the need for safety bubbles especially on the platform lemmy which is pretty outspoken and overwhelmingly leftist. These issues should be visible to the general public to make them aware, not segregated in their own vicinity where no one else is allowed and will lead to hyperfixation and very likely discriminatory viwepoints and discussions.
I have taken a look at communities like twoXchromosomes, childfree and incel and the language they use sometimes is eerily similar to nazis and faschists. Tribalism develops really fast and it is NOT a good thing. Too many times I’ve read stuff like “today I completely destroyed <target enemy demographic>”. In the case of twoX it was men, in incels it was women and in childfree it was moms. These communities were formed out of a legitimate point of unacceptance and ignorance by the average person but longtime segregation effects are starting to take hold. The LGBT+ is also starting to show these effects and I don’t really like it tbh. I’ve honestly been denied entrance to publicly advertised events and happenings just because I wasn’t “gay” or “queer”. This will not foster acceptance. Especially not in a space where no one cares or knows what you are. I mean programming is about the most equalizing activity ever. Job environments and work teams are still suffering from ignorance but the programming itself is equal and especially online you should not segregate the community. Imo.

Yeah, it seems that a space like this is trying to be exclusive rather than inclusive.