1. The crazy ideas jacquesm decries have a limited influence on one's life. Those are (predominantly) singular topics rather than all-encompassing ideologies. They are more of conversation starters than life guides. Aside of some rare dangerous ones (COVID-19 theories perhaps?), their impact places somewhere between stamp collecting and junk food consumption. All the flat earthers, the 5G's, the moon landing hoaxes etc., - let people have weird hobbies. We can handle them as a society.
2. Given how prevalent conspiracy theories are - across times, cultures, geographical locations, social niches - I posit our propensity towards them is not a random fluke of human psyche. No, I posit the conspiracy theories play a role in some other societal processes. I posit that trying to eradicate or suppress the underlying mechanism, without understanding the mechanism in the wider context of all societal processes would cause unforeseen negative consequences.