About the only time it'll be good for the integrity of professional chess that no-one cares about the women's events https://t.co/Np0MzYcc6n— Andrew Pearson (@adrwtp) January 26, 2016
I don't think many people in the chess world intend to be sexist - much of the more blatant sexism is of the "benevolent" kind - the tournament livestream watcher who, writing in, addresses the commentators as "wise Peter and beautiful Sopiko", for example. But the demographics are very much male-dominated, and the culture surrounding the game reflects that - not helped by the fact that FIDE, the game's international governing body, is one of the last remaining bastions of the USSR.
Perhaps because of this culture, perhaps because of sexism in the communities from which chess players arise, perhaps because men tend to think more analytically, and perhaps simply because men tend to exhibit more variation than women in their abilities, there are vastly more strong male players than female players. Hou Yifan, the strongest female chess player in the world, is the world's 68th strongest player overall. I don't know how many male players are stronger than Humpy Koneru, the female no. 2, but a bit of extrapolation from the ratings at the lower end of the top 100 men suggests she's probably some way outside the top 200.
This means that there are a great many men who could potentially choose to identify as transwomen and compete for the women's world championship. I can definitely imagine some men doing that to become Women Grand Masters, the bar for which is set considerably lower than that which exists for Grand Masters proper, but I think it's unlikely to happen for the world championship.
Firstly, success in top chess tournaments has a lot to do with preparation. Magnus Carlsen, not a player noted for his strength in the opening, had no fewer than four grandmasters helping him on a daily basis during his last title defence - three of them "Super-GMs", members of the elite group of fifty or so of the world's very strongest players. (Only one woman - the great Judit Polgár - has ever been a super-GM). I imagine that it would be easier for someone uncontroversially accepted to be a woman to find willing aides than someone who might be seen as a huckster.
Second, and perhaps more fundamentally, people don't really care about the women's events. Judit Polgár was the undisputed greatest female player in the world for over 25 years, and never once bothered to compete for the title of Women's World Champion. Hou Yifan's dominance of the female chess world is not as total as that which Polgár had - though still very solid, even more than Magnus Carlsen's domination of the men's game - and she is a past Women's World Champion, but at the time of the most recent Championship she simply didn't bother to compete. Granted, it was because of a clash with another tournament, but the tournament she went to wasn't especially high-status either. To Kirsan Illyumzhinov and other bigwigs at the Federacion Internationale d'Echecs (FIDE), such events are an extra source of kickbacks. To everyone else, they're just yet another low-level tournament, reports of which tend to include rather more pictures than normal.