> it's felt very true as audience size exploded
I think this is the key point. As with most issues on the internet, it's mostly an issue of scale. I assume these problematic users are actually only a very small fraction overall, but as the overall size grows, so does the number of people who belong at the very edge of the bell curve in terms of "normal" behavior.
With scale, any rare issue becomes common enough to be annoying.
I can't remember who I stole "the internet is write only" but it's felt very true as audience size exploded.
Perhaps the worst part is that it's self reinforcing in either direction, and few people ever leave the agora unless they delve into niche subjects, so they bring the agora mentality with them.