My Goodreads friends are a mixture of IRL friends, current and former coworkers, and a handful of random people who sent me friend requests out of the blue that I accepted (I don't do that on other social media, but on Goodreads it's whatever). I think a lot of other people find friends by joining groups.

Seems to me like most of the accounts I run across with high friend/follower accounts are people who deliberately cultivated a large following because they are book bloggers. I have no interest in becoming one of those, and their reviews will always display before (and therefore help to hide) mine, so I just write my reviews for me. If someone else finds and enjoys my review that's cool, but I don't expect it.