I ask myself this question a lot these days. How could I basically be clueless for that long? I wasn't really clueless, it was just survival.
Over a certain age, there was no information, no access to it, and no way to even know what to look up if I even had had access to it. By the time it really showed up in things like media, we could see it was portrayed so darkly or negatively and we were old enough to realize that we better keep it to ourselves. A dark secret. I think most of us in those age groups kept hoping we'd be cured by love or time, or age, or maybe just that no one would find out, lol. It never occurred to me that you could live like this. Later, its like, oh young people have it so good, but I'm not young.
And all of that happens in your head on a sort of subconscious/conscious level. Then its put back again where no one can see it. I really believe its just like drug addiction denial or eating disorders. You can convince yourself of anything. Do something outright, convince yourself you don't have a problem, and then act and believe it never happened.
I was 10/11 when I started cross-dressing and realized that I was sexually fluid the first time. I was always fascinated by everything girl though. I messed around with other gay and bi boys in my neighborhood, but I realized pretty quick no one else wanted to BE a girl and then a boy I messed around with freaked out afterwords and told everyone.
It was pretty horrible in this state to be any kind of queer so I started obscuring who I was, total damage control.
I still crossdressed, had urges, envied girls... I remember shaving my legs all the time, thinking about how girls had it all and I'd give anything to be one. Thinking if I wished hard enough.... if I really believed, whatever controlled this universe... god or whatever would grant me the kindness of turning me into a girl and changing everyone's memory of me. For a long while, I thought I just wasn't trying hard enough to believe, lol.
Then reality sets in and you realize your stuck and I thought I was crazy, quite honestly. So I went about obscuring everything to the max. I got called the F-word (the gay slur) all the time. Every time they critiqued something, I changed it to adjust my flamboyance from noticeable to camouflaged.

Then it was just slowly putting everything in a box and sealing it. Egg state. Total closet. It was total denial. I mean I asked several girls I went out this much later with and it doesn't look like much each piece and part but together makes a rather convincing picture of closeted living. Especially with all the stuff they didn't know, those are convincing on their own.
Then you're just basically running down a clock on how long you can take living closeted before it starts taking too much of a toll.