A general rule, I think, is that people don't make friends with people who are smarter than them. By smart, I don'y mean book smart, rather native intelligence.
Used to travel a lot for work, involving meeting a lot of people. Some people, and race, ethnicity, etc., played no role, were just immediately my friends. It didn't happen a lot. Can't really explain it, but after that I never worried about friends because I figured it became something that would happen without any conscious influence on my part.