I'd say it's that we all have these elements within us.

We're all born as selfish idiots, how can we be otherwise? We're helpless at birth, thrust from perfect comfort and safety into discomfort, utterly ignorant and wholly dependent, with no knowledge there are others, who are just as dependent when they're born.

There's the variability in personality, but by and large we have to learn to see others as the same as ourselves.

So while we may not all actively try to be assholes, it takes conscious effort to be better than our base nature.

And, I tend to think we all get to be assholes now and again. We all have moments we can look back on and say "oh, yea, I was the asshole that time".

Social media just reflects humanity, though the algorithms are certainly designed to increase engagement via the simplest mechanisms - emotional engagement. And which are the easiest to target? Yep - the most basic, they have the broadest appeal, because we all share those base emotions.

Another way to look at this: if we didn't share these base emotions, would the algorithms have any effect?

World Hunger is literally a problem of corruption. The vast majority of problems are "we could solve this, but it costs money and we'd rather have another mega yacht". If humans were truly altruistic, homelessness and hunger wouldn't be issues at all. Are we savages? Maybe not. But overall altruistic? Bullshit.

There's a reason we idolize heros instead of treating them as mundane. They are exceptional, not the norm.