Cliques (which is what you’re referring to) in tech and corporate environment in general are common and not necessarily a bad thing. For example, a lot of early google engineers came from dec (sanjay, jeff) and ucsb where urs was a professor as well as stanford (both founders and first employee). Seems like it worked out well for them. It only becomes toxic if they develop a hive mind and start to actively bash/drive away “outsiders”