I very many times have insecurities of being smart or not so I bury myself in topics (like pop psychology) to get the social gratification of being "smart".
You've answered the main question perfectly on your own. I'll just add that it stems from a deeper cause: for us to fit into the tribe, whichever tribe it is that we want to belong to. Being accepted feels good, and being cast off feels terrible. It is, of course, a more complex and interesting topic than that, but I'll leave researching it to you because I don't have the energy to dive into it.
Finding an intellectual equal and enjoying their company is one thing; circle-jerks are another. They're both gratifying in nature, but where one moves you towards thoughtful discussions and rewards you for using your intellect, whatever it rises towards, for good, circle-jerking is using your intellect as a pedestal to make yourself appear to be bigger, more important than those puny stupid other humans, which promotes inequality and swelled egos for the jerkers and anti-intellectual ideas for their targets. Needless to say, neither is helpful or useful.
As for "smart" topics -- Here, in Russia, knowing a second language is considered to be a sign of a clever person; a third language and beyond will make many people talk about you in awe. Things like advanced natural sciences are perceived as beyond the ability of a normal human being; where I live, even knowing physics rings a nerd alert - which is to say, I don't live in an academic neighbourhood. From that pattern, you may figure out the rest.