You cannot equate ancient and near-modern examples of men castrating themselves (or cross-dressers) with late 20th-century trannies. The former did so either because of religious conviction or economic expediency. You don't read records of them claiming "I've been living a lie all along. Now I've found my true self", as modern trannies invariably do. And such existential reflection is good evidence that trannyism is a thoroughly modern phenomenon. It is related to the search of authenticity, the search of how to live life. Before modernity, religions and traditional communities told people how they should conduct their lives. People took it for granted that their lives are a pre-set template, and it didn't even occur to people that there are other options. It is only when religions fail to hold sway, and people had lost their ties to tradition, did people begin to realize that they have the freedom to choose how to live. People found out there are many many ways to create meanings in life, and that they can start living a new life any time as long as they have the will to do so. Some men, then, chose the freedom to live as women.

But why choose to live as women? I suppose Feminism (especially Third Wave) has mystified womanhood as the exotic "other" which appeals to the adventurous spirit of some men -- attaining womanhood is, in essence, a quest for the Holy Grail. If what I say is true, then trannyism is, paradoxically, motivated by a stereotypically male drive for conquest. This may explain why MtFs widely outnumber FtMs.

I can find ladyboy porn going back as far the 80s). How can "traditionalists" unironically claim transgenderism is a recent phenomenon.
I don't know much about Thai culture but it seems the phenomenon of Ladybois have strong social and economic roots. I'm not convinced they are exactly comparable to Western troons. Also 80s is very modern.

The Amsterdam Cohort saw a 20x rise of clinical cases of transgenderism in Netherlands between 1980 to 2015.