Ratio

In order to understand the transgender condition one first needs to comprehend how much people are products of the combination of nature and nurture.

Most feminine men and masculine women generally do not have strong enough cross gender identification to act upon it however some ponder over it. Lyne is a lesbian woman in her mid 40's I have lost touch with but she shared with me her mulling over whether she was in fact a transgender male. She was very masculine presenting and acting but in the end she decided there wasn't enough there to warrant a change.

The gradient of masculinity and femininity produces people people who are drastically different and although some would have historically "crossdreamed" (tip of the hat to Jack Molay) there was no recourse in the past to do much about it. Certainly not before the 1930's.

I am assuming that today's transgender people represent those with a cross gender identification strong enough to require a response. I am also betting that this ratio has probably been historically constant except nothing could be done about it. Prior to the 20th century,  the most extreme cases would have simply had to settle for attempting to live as the opposite sex. Of course right wing idiots would have people believe we are only a recent invention

Zagria has plenty of examples  of historical figures on her site.