The issue is twofold here. The first problem is that this involves confronting someone you've already entrusted your life to, which is something that'd be difficult for most modern men, let alone women. The second problem is that guys who do things like this generally sit in liberal circles, and breaking up with your boyfriend/husband while simultaneously being "outed" as "transphobic" to all of your "friends" is a really, really rough prospect. Especially since all of the politics she's trusted up to this point tell her to tolerate it, and the incentives too. At that point, she's now a divorcee in her let's-be-optimistic-and-say-30's, with a crazy troon badmouthing her every way that he can, and she's got to navigate a field that's been picked clean of anyone desirable.
As rough as things are in the male dating market, I can have some sympathy for women here. The options are to age into a resentful empty egg carton meme or to figure out a way to invest her youth in a guy who is neither a cad aiming for an easy lay nor some variety of freak-in-waiting. If you don't have a pre-existing community that makes these things happen for you by promising to shun people who cheat, troon out, or initiate a midlife crisis divorce, the relationship game is a scary place.