The phenomenon on display in the Facebook search result screenshots is known in technology circles as a “data void”, after a paper by the Data & Society founder and researcher danah boyd. For certain search terms, boyd explains, “the available relevant data is limited, non-existent, or deeply problematic”.

In the case of vaccines, the fact that scientists and doctors are not producing a steady stream of new digital content about settled science has left a void for conspiracy theorists and fraudsters to fill with fear-mongering propaganda and misinformation. [...]

Pinterest has responded by building a “blacklist” of “polluted” search terms.

“We are doing our best to remove bad content, but we know that there is bad content that we haven’t gotten to yet,” explained Ifeoma Ozoma, a public policy and social impact manager at Pinterest. “We don’t want to surface that with search terms like ‘cancer cure’ or ‘suicide’. We’re hoping that we can move from breaking the site to surfacing only good content. Until then, this is preferable.”

YouTube is crucial part of the misinformation ecology. Not just a demand issue: its recommender algo is a "go down the rabbit hole" machine.
You watch a Trump rally: you get suggested white supremacist videos, sometimes, auto-playing. Like a gateway drug theory of engagement.
I've seen this work across the political spectrum. YouTube algo has discovered out-flanking and "red-pilling" is.. engaging. So it does.

“I started the site for a easy way to make money,” said a 17-year-old who runs a site [from Veles] with four other people. “In Macedonia the economy is very weak and teenagers are not allowed to work, so we need to find creative ways to make some money. I’m a musician but I can’t afford music gear. Here in Macedonia the revenue from a small site is enough to afford many things.”