It's understandable. My method is actively see more people; online it's much simpler. Then get an idea of their interests, and if we share some of them, to try to communicate regarding these things. Soon enough you are somehow acquainted with a number of smart people. Even if few will become your friends, you keep learning from them, and keep getting leads to other potentially interesting people.
Try to frame it as an engineering task of a graph traversal optimization. Also, you have to be open; no people are going to check all boxes. Limit the filter to really important stuff.
...wait, that sounds like I mean that I think I'm really super smart. That isn't the case, I just don't meet many people, and those that I do meet I don't think are clearly brighter than me. The ones that are, usually don't really seem interested in being friends, so whatever.
Turns out these things aren't so simple as random people on the internet claim.