“My question is how do they find each other?”
The internet has certainly made it easier.
You might recall the German who advertised on the internet for someone to kill and eat him. And he found someone who did.
This happens on part of internet that most people don’t know about, and don’t need to know about, where characters like this can find each other.
If you think that the normal worldwide web is bad you simply have no idea of what level of depravity our alleged fellow human beings are capable of.
Sebastian Maniscalco has a good bit on how the internet allows weirdos to come out of their basements.