everybody and their dog had a pirated copy of flash back in the day. i'd bet that there were more users of pirated flash back in the flash gaming heyday than there are unity users today.
I do remember a few kids in high school that were Flash pros pretty early on (as early as 14). I don't recall those kids moving on to actual game development tools. There must have been something very friendly about Flash's onboarding. I'd be curious to know what the equivalent is for kids now days (would be surprising if its Unity/Unreal/Godot). Sort of asking for myself here because I can't for the life of me grasp the UI driven development of Unity/Unreal/Godot.
14 would have been about the age i was playing with it too. in my memory, the magic of flash studio was that you could make something so immediately. it worked well for simple things, you didn't have to make a full-on game, a bunch of kids in jr high computer class could actually make something cool in the length of one class.
The onboarding was that you just start key frame animating and pasting in actionscripts.
I think the fact that it was (acquired early and) developed by the PDF company must have had to do with it. Stupid Flash files were everywhere, but Flash contents that are seriously disappointing from artistic perspectives were rare.