As someone hearing about this only now, what actually happened? I find it extremely difficult to believe that the FSF fired anyone based on any one trait. This

As someone hearing about this only now, what actually happened? I find it extremely difficult to believe that the FSF fired anyone based on any one trait. This post says that the trans person "stood up for themselves", and because of the ambiguity, this makes me think that it might not have been as simple as all that.