Well, since the topic got bumped, I may as well throw in my opinion.
I reckon that the actual number of CAMAB and CAFAB trans* is roughly equal. The reason it seems like most are CAMAB is because many statistics only factor in those that have had bottom surgery. It's well known that women are more likely to get bottom surgery than men - the reasons for which are two-fold. First of all, obviously neovulvas/vaginas usually resemble natural vulvas/vaginas more so than neopenises resemble natural penises (and with phalloplasty, there's a big risk of losing sensation, whereas with vaginoplasties the risk is pretty low). The second reason is that women are under a lot more pressure to have a vagina than men are to have a penis. In a society which regards the female body as a commodity, something for men to consume and objectify, not having the 'right' genitalia brands you as a failure. With the male body, which isn't objectified to nearly the same extent, there's less pressure. So ultimately, many trans women who wouldn't otherwise particularly want bottom surgery are getting it anyway due to societal pressures, which is less frequently the case for trans men.
Now with regards to why trans women have so much more visibility. The lion's share of representation of trans women treats them as either a punchline or a monster. Again, the reasons for this are rooted in misogyny. In a world where men are seen a superior, and women consequently as inferior, the idea of any male choosing to be a woman (N.B. obviously for most trans people it isn't a choice, but this is from society's point of view) is seen as absurd - why would someone born into a 'superior' class want to associate themselves with a class that is 'inferior'? Because trans women pose a very real threat to the idea of male supremacy, there are two ways in which they are defamed. The most common way is to portray them as having an incentive to attract unsuspecting hetero men and sleep with them, thus representing the one facet of life in which misogynists see women as having power over them (i.e. by being sexually attractive) - they are regarded as deceptive and perverted, thinking of nothing but sex. The second most common method is to portray them as evil or otherwise mentally ill - thus, their 'desire' to become female is seen as being rooted in their being 'crazy' (which in itself is a function of ableism - a topic for another day). In these ways, it's insured that trans women are never taken seriously, and male supremacy stays unchallenged.
By contrast, trans men do not pose nearly as big a threat to male supremacy. Because from a misogynist's standpoint, why wouldn't someone born into the female class want to 'emulate' men, the 'superior' class? While trans women are pathologised, trans men can be mostly ignored by society, because being male is not seen as inferior. They will still often be dismissed, of course, but there is no need for such a concentrated effort to mark them out.
One last thing to note is that trans men often have a much easier time assimilating into society (i.e. becoming 'stealth') than trans women do. This is partially due to the nature of HRT (in particular the way that testosterone induces facial hair growth and a deepened voice, whilst estrogen does not reverse this), but a much bigger reason is due to the way we subconciously gender people. It's something that almost everyone does without even thinking - within seconds we will have formulated whether we see a person as male or female based on their physical appearance. Most people do this by looking for male traits - those with them are regarded as men, whilst those without them are regarded as women. This stems from the cultural perception that men, as the 'superior' class, are defined as 'having' something, and women are defined as 'lacking' that same thing. Aside from visible breasts, almost every gendered trait we notice most is a male trait. Facial hair, an Adam's apple, M-shaped hairline, wide shoulders etc. - the presence of even one of these can be enough for someone to gender someone else as male. If the person in question has more than one of these things, they are even more likely to be gendered as male. Couple that with the fact that women in general are scrutinised for their appearance much more so than men, and you have a culture where 'passing' is much more difficult for trans women than trans men.
So long story short, the reason CAMAB folks get so much more visibility than CAFAB folks is out of a need to pathologise everything related to the 'female' class.
