Really? Think about it: when you befriend a new person, was that person usually a complete stranger to you before, or maybe rather a friend of a friend?
The important bit is "people you know from the internet".
For example, I really like survival horror and horror-themed action games. That's what connects me with one particular woman who shares these interests. However, she's also into My Little Pony and other furry stuff. I don't care about those things or people from those circles.
All those communities are very narrow in focus. They only share one particular interest.
Really? Think about it: when you befriend a new person, was that person usually a complete stranger to you before, or maybe rather a friend of a friend?