Normal, grounded people don't wake up one morning and go "I get it, the Jews and Soros are conspiring to suppress the truth about the Flat Earth", they get there by baby steps, each one veering more and more into the illogical.
Maybe it was when they were unemployed or in medical trouble and stressed out beyond their ability to cope, then wanted explanations, however implausible, that gave them at least an idea of what was wrong with their world. From there it took root and by degrees they slip into this other world of nonsense and batshittery.
Crystal therapy and detox can lead to healing rituals can lead to cults can lead to suddenly selling everything and donating it all to some fraudulent healer.
Like you observe, I think we're all in need of a best friend, family member, or spouse who can say "You've got a problem, this has to stop now."
The problem with the internet is it delivers. If you want to know more about quantum physics or molecular biology or cancer research you can dig and dig and keep on digging, you will never run out of material. Likewise if you're looking for harmful material, it will unquestioningly keep going all the way.
If Google started to detect the pattern of someone slipping into madness and did what they could to start to refute things, to sprinkle in some helpful counter-points with their diet of pure nonsense, maybe we can save people who'd otherwise be lost.