I believe there are several factors.
1) TG is becoming the frontier of 'Cool'. AKA different. AKA, messing with the old folks heads
2) It is less hidden in general. Over the past 50 years ago, to which I exceed that number of years, the world today is like a totally different alternate universe then the 1960's/70's when I first "Experimented".
3) Most important factor for the seemingly "Increase" is The definition. Back 50 years ago you were either a TV or a TS. Drag Queens were simply gay guys in a dress. TV's straight (AKA 'Normal') guys in a dress. And then the total fringe element, most guys (as in doctors) could not relate to, the Nut Whackers that wanted to make their junk disappear. Today TG is a VERY large umbrella term encompassing anything from 100% Cis-Female to Cis-Male.
4) Identity Politics - Part of the above #3. Make the definition broader, more inclusive, and there is power in numbers.
5) Social Media, part of #1, being cool
No way can this life long chameleon believe the stat that upwards of 0.5% of the overall population is TG. Broadly speaking, maybe. Depending on the criteria. Age group will skew the results. Broadly speaking 60-50 should be about the same as 50-40 as should be 20-40. Somehow I mostly suspect this is not the case.
Of course, my Luddite, conspiracy theory self can blame a lot of "Food Science" and too early immunizations in the western world, and other 'Life-Style' issues as a factor in skewing the numbers for younger people. For anyone with just a small exposure to the miracle of embryonic development, there is SO much that can easily go wrong. And then there are the so-called "junk genes" which, IMHO got to be there for some reason. Even if was just for one step during embryonic development. When you consider how we start out as fish in the womb and wind up as people.....
I often joke that just as with Teenage Mutant Ninja Turtles reveled to us in "The Secret of the Ooze" that their birthplace was Bayonne, NJ; my home town; that there must be something with the water. Perhaps the seemingly increase of TG is due to environmental and pre-natal development factors. Every bit as much as I may be a DES baby. Can you say PBA Baby? Or HFCS baby? Or.....