> Facebook is not a publishing house (at least not the Facebook social media platform as such) and mandating that they fact check and curate their ads and content is tricky business.

This is not by force of nature; this is the result of laws and policies that people created and that can be changed. The safe harbor provisions that exempts internet service providers from liability for user generated content created the circumstances that led to the creation and growth of huge companies like Facebook. But it doesn't have to be that way: in another world where all publishers (internet or other) would be liable for all content on their platform, companies like Facebook would never have existed, we'd probably have many smaller and more local publishers, economically less efficient but having much less of the current disinformation problems.