Online friend groups are created more through repetition than anything else. Literally just joining a discord and be there at the same time every day brute forces you into a friend group. Honestly I think a lot of offline friend groups are created through this repetition also, a bunch of people sharing the same interest on the same schedule often becomes a friend group of convenience. The thing with online is that you tend to get out of it what you put in, if you're invisible and lurk you don't gain recognisability in the group and don't tend to do stuff with other people as a result of being considered an active group member. This also kinda requires the group to actually be doing stuff too though, and some of them definitely don't.