LGBT as a category has been increased a lot over the years. Asexual or people who don’t feel they conform to super strict gender norms are all included as “queer” now. So I imagine it’s a combo of things, some people being trendy, some people being freer and not feeling the need to hide, some people who previously didn’t identify being included.
Left handedness was persecuted and after it stopped being persecuted there was a massive rise in people who were left handed. But it plateaued and has remained pretty stable since then.