It's quite possible that they just went and built them. It's not rocket science, and other cultures have done the same. Or were the folks in the New World just somehow dumber than everyone else?
If there are thousands, it ought to be no big deal to show me a few dozen of them. Start whenever you're ready. Let me know when you've given up.
It's quite likely that they didn't come from anywhere, because they don't exist. If they do, let me know where I can see some of them. And if they do exist, that's a good question...where did they come from? It's not like other areas were plagued with red-headed giants.
What would be their motivation for that, in your opinion?
Alternately, the post-AOL internet has given various whackadoodles easier access to one another, and nothing accelerates crazy quite like more crazy. There were far fewer crazy and stupid people on the internet back in the nineties, when it actually took some know-how to get there. (Perhaps they were crazy too, but they didn't show it like crazy people do today.) Egalitarianism has its drawbacks.