My theory is that as people get more success in life, they tend to get "busier". They have families, careers, hobbies they've invested time in, money to take travel vacations, etc. They just do more "stuff". This results in less time and interest towards getting into arguments with randos on the internet.

The internet is extremely accessible and economically inexpensive though, so almost everyone can get on here if they want, regardless of any personal degree of any sort of life proficiencies.

Together, these factors result in it being the mass of humanity with some of the cream skimmed off. So that's what we tend to see around us, the internet is the skim milk of humanity. Then to avoid all the watery garbage so prevalent everywhere, we further clump into more segmented communities where we can find more like-minded people to associate with, simply because that's more enjoyable.

This is one of the reasons I think it's important to actually put effort into interacting on here, to try to help prevent it from worsening before we can address some of the underlying technical problems it has introduced into our societies.