I dont have dates for this but of course in theatre men depicted women for years, and then after women were allowed to perform, men playing women in pantomime became another tradition.
Drag as part of gay culture is part of a time when both gay men and lesbians were influenced by traditional mainstream culture that many conformed to the idea were either butch or femme. So the fact the some gay clubs had men performing as women both as a sort of homage to women with over the top female clothes and make up and an opportunity to be feminine was and still is nothing to do with saying you are the opposite sex to the one you were born. Any more than a lesbian wearing a man's suit is a man.
And in the 70s when Women's Liberation was challenging gender norms, to dismantle them not to entrench them, drag acts were sort of applauded for doing that. ie challenging gender norms because they clearly weren't saying this is real, it was about performing gender roles in an exaggerated way.
The big change was when queer politics coopted gay and lesbian culture in order to undermine it, in the same way as it had done with women's liberation / feminism. (There are lots of threads about this, but because mumsnet technology doesn't allow tagging or categorising it takes a while to track down.)
At its simplist queer is about dismantling anything that was or is seen as being the norm.
So this queer gay culture that has led to Pride parades, far from showing that every day people are gay and lesbian (ie no dressing up) has been turned into a vulgar over sexualised display of predominantly men wearing S&M style of dress and fluanting body parts. This meant that drag queens were / are comparison more acceptable, and building on the pantomime Dame tradtion, opened the door to Drag Queen Story Telling.
And also turned what used to be about a small group of people with gender disphoria into a trans cult because queer politics expanded it to coopt and colonise the idea or feeling that people could claim they were the opposite sex.
So as the (usual well researched) earlier posts on this thread have shown, when stonewall was what it was set up to be, Gay Liberation, this whole "umbrella" approach didn't exist, because is Gay Liberation was about same sex attraction.
Identies or "changing sex", had nothing to do with it, because of course if sex isn't fixed then there cant be gay men or lesbian women. (which is why I always find it so strange that some gay men and lesbians happily associated with a politics that actually says you dont exist).
JUst think if the 70s gender benders had only grown and expanded so it became the norm to wear clothes that previously had been said to be the "uniform" of one sex of the other, how none, well at least some of this, would never have happened.