This is a good point - 'there have always been transgender people' - changing the terminology, there have always been men who presented as 'feminine' and women who presented as 'masculine' [using gender stereot ype shorthand there!].
I asked some older relatives about this a few years ago, and they could remember from their childhood a man down the street who wore make-up and used a woman's name, and elsewhere a woman who only wore men's clothes, swore like a trooper, and drank pints with the lads in the pub.
It was clear that they were tolerated, nobody did them any harm - but they were regarded with a combination of amusement and pity.
The idea that a movement comprising a very small number of similar people could alter social, political and cultural life to the extent the trans movement has is astonishing, and as Tiredofwhataboutery says, would it have been possible without the megaphone of social media?