People want to belong to a tribe. I think it's often quite a tossup where a young person ends up, depending on friends or whichever online circle accepts them best. It's also not rare for young people to flipflop between nominally widely opposing tribes before setting into one. People gradually learn all the opinions they are supposed to have on the various issues to truly belong to the tribe. It's not unlike learning the dogmas of a religion. It's much much more convenient socially to speak the same language and have the same cultural references and opinions to bond over and feel camaraderie about and curate a bubble of friends following the same opinion-setters, vs. creating one's own grab-bag idiosyncratic set of opinions that doesn't fit neatly into either well known combo-deal. You gotta support either this football team or the other one. People who start to lecture about how they like the goalie of the one team, but the striker of the other are just "not fun at parties", are kind of annoying and hard to relate to, especially online where people decide in a split second whether to upvote or downvote based on a fast pattern matching check to my tribe / enemy tribe.