As to your original question I think the internet and its verisimilitudes have much to blame for that. It's allowed marginal groups to band together with common interest and intent and has given them power and influence. There have always been trans people, for whatever reason, and society has always made space for them.
I think what's happened is a horrible and perfect confluence of a number of things. An overly monetised and commercialised society, identity politics is an extemely capitalist ideology even if the proponents do not wish to see it as thus. It's intensely individualistic and relies upon consumption for 'people to live their true lives', this feeds into our current economic model so is encouraged by invested parties.
At the same time stratiefied notions of gender are also encouraged by a capitalist society as it stimulates 'need' in people to buy products that we're told we need in order to be women 'properly' (make-up, hair-removal, hair dye etc etc). So it's now an easy con to say if your interests fall outside the very strict binary gender roles that have been latterly imposed there must be something wrong with you, it can't possibly be the straitjacketed society that has imposed roles upon you that's wrong, it must be you, and it can be fixed! With money (and the hormones and interventions that it buys).
Finally, and most prescient, I think is men and male sexuality and the significant number of men who feel entirely entitled to fulfil themselves sexually at 'no matter what cost', it's been the case since time eternal that women have been kept down by dint of biology, we're not as strong, we carry babies and for thousands of years we had no control over conception other than refusal. And that refusal wasn't always listened to. And it's still not listened to. And the fact that the internet, the crown on human achievement, a place where, if you have the desire, a repository of all human knowledge, can find any studies , any wisdom, anything a-fucking-tall, is primarily used for looking at porn is depressingly telling about how men and their need for sexual gratification is utterly primary in pretty much every level of society and how it's shaped.
So the whole 'trans thing' has emerged like a giant fucking maggot from a pile of festering shite. Blind but voracious, it doesn't care what it devours to reach its end. I don't think many people have noticed what's been laid by a few very wiley flies.