If you know exposure to radiation causes cancer, then you shouldn't let people continue to mine despite simply wanting more uranium or what have you for philanthropic purposes.
You seem to be confusing correlation with causation. Correlation is effectively coincidence. You can't expect anyone to make decisions - business or otherwise - based on coincidence. In fact, we attemp to solve too many symptoms based on correlation. We can't keep doing that. It's creating more noise while true root problems continue and expand.
The irony is that these machine learning algorithms are effectively coincidence machines. There's no rhyme or reason as to why they work once you have even just a handful of neural net layers, and people invest quite a lot into these magic recommendation machines.
As for toxicity, I don't think there's one magical root cause for all of it. And I'd argue that most features and designs to increase engagement _are_ one of the many causes for people to create lucrative polarizing digital content.
edit: Also I'm not sure how my original post was confusing correlation with causation. You can replace "correlation" with "coincidence" there without issue.
They're tuned to increase engagement. They figure out based on inputs what does that. There's no morality, no value judgement, etc. They try to increase engagement.
Why toxic (which is subjective) appeals to so many humans is really the question here. The algorythms has no say in that.
A coincidence is a good starting point for discovering things. A natural next step would be to figure out how to dissect trained networks and turn them into proper models.
I hope we can figure it out! I'm a big fan of explainable AI initiatives. Though I have a feeling it won't be for another decade or so before anything huge is discovered, considering how long the technology has been around.