IMO this is because Lemmy is still mostly targeted at techy/open source people. Trans women have already created their own communities/subculture in this world (‘programmer socks’ etc). But there’s not that critical mass of trans men programmers to make a bustling community here.
Lemmy is probably also very white.
So we need more diverse topics to attract a more diverse audience. Right now, the only people signing up for Lemmy are people who have opinions about Internet protocols.