There'd have to be a lot going on to hide that. If acknowledgement and "treatment" of transgenderism genuinely leads to fewer suicides, all other things being equal, the general suicide rate would decrease with it.
This is not true, once you consider the statistics.
Transgender people are very rare and the suicide rates for transgender people, whilst higher than the general population, are still overall low. This means that suicides of transgender people comprise a very small proportion of the total population suicide rate. You couldn't pick out changes in transgender suicide from the background noise of the total population rate.
Your position here includes at minimum that:
A) There were always transgender people, but they were oppressed and written out of history.
B) They've always been in despair, but their conditions would be included in more generalized descriptors and their suicides would be hidden in general suicide statistics.
C) The acknowledgment and treatment of the condition has prevented many suicides, but you can't actually see that drop because the general population was increasingly killing itself.
A)
Understanding of gender is complex. There is evidence it was never as simple as monolithic, fixed, binary gender. Even in our traditional Greco-Roman-based culture, there are some indications of muddied waters, such as eunuchs (who were male sex, but were in some contexts treated as female). There's plenty of evidence of cross-dressing. In some Asian cultures (e.g. Japan, Thailand I think?) there appear to have been groups/people which may not have readily been understood as male or female gender. These may well be reflections of transgender or non-binary, formed by and relevant to their place and time. So when you say they were oppressed, I might say "not always".
And when you say written out of history, I would point out that virtually nothing about humanity was recorded for most of history. We probably have more written output from 2024 than we have from all the years up to 1900 combined. Most of what was recorded is the "big stuff": politics, religion, philosophy, etc. The lives of ordinary people is almost entirely absent - few writers cared enough to record it. That they would record a marginalised group even less likely. And yet even still we do have hints that transgender and non-binary may have existed, albeit through different cultural understanding and expression.
B&C) Already addressed.
It's not proof, by any means, I understand that, but every piece of information you have to explain away with credulity makes the sum total even more incredulous.
...
How many things need be undetectable before you start entertaining the possibility that there wasn't anything to detect?
It's nice that you recognise that a correlation is not proof, but if you are hanging an argument on a peg of your own credulity, what grounds do you have to criticise anyone else's?
I am minded of reading comments from a (I think) Ugandan, who said that homosexuality was a white man's disease, presenting as argument that was no homosexuality in Uganda until the white man arrived. There are a lot of parallels between his argument and yours here.
en.wikipedia.org
