It's almost certainly because of the tankie factory that is .ml and the fact that it's admins are all hard core tankies (including the main dev! And ofc the whole infamous Nutomic transphobe incident)
Coupled with the fact that a few of the biggest communities are on .ml does not bode well.
That's why I keep calling for a general boycott against posting content or comments on .ml communities.
.ml doesn't want growth, they want a tankie echo chamber, if anybody wants to actually see Lemmy grow at a healthy pace it starts with shuning the hostile tankies and their instances.