Because internet didn't existed back then to congregate and enable people to say whatever they want.

Before you could be that stupid, but probably would be the only one in your neighborhood so any stupid thoughts would be kept to yourself until you eventually move on, but now if you think earth is shaped like a half eaten donnut, you bet your ass you will find a community of other weirdos with that same belief and they will feed themselves more stupidness and become louder and louder.

Honestly I'm one example myself, when I was a teenager back in the 90s/2000s I really liked those Japanese emo style music(Visual kei), but since no one else around me had ever heard about it and no one was interested on it I had no one to talk about it, then I just moved on, but if it was today I have no idea what kind of creepy teen I would have become, honestly for me it was a blessing haha