In the past most, especially school aged children and college age adults, needed to carefully craft your acquaintance group and police them through concerted effort, sometimes over years, to get a self-selected group who would challenge you so little. Now all the work is done for you using data you’ve been submitting for review literally the entire time you use the internet.
The real tragedy for me is how many kids and adults go online out of curiosity on a subject and end up on twitter, or facebook, or YouTube. The curiosity gets replaced with seeking those dopamine hits from endlessly scrolling.
Edit: dont forget youtube.
Imagine you have a history of buying into hysterics (or “enjoys controversial science”) and are curious about astronomy, or politics. Log on to youtube or facebook to find communities where people are discussing these topics and you’re directed to flat earth, and qanon, pol pot fans, among others.
These established groups are full of people who will tell you whatever you were on about is dead on, any time someone comes in and shares evidence to the contrary can be banned so you don't need to think about it anymore, dogpiled on so that their responses become less and less informative, accused of brigading. All this gives you a good out if you'd like to avoid being challenged and just straight pulling in those dopamine hits.
Again you can do this in real life but it takes work to keep and maintain an echo chamber in the real world. On social media you’re effectively automating away the problem.
Edit: don't forget about the tankies