This point, "<i>my surprise is consistent with the fact that people poorly understand each other, all too often</i>" reminds me of a quote that was attributed to Kurt Gödel.  He reportedly said, 
> “The more I think about language, the more it amazes me that people ever understand each other at all.”

And Gödel ties into conspiracy theories, too.  I seem to recall that he died by starving himself to death because he thought that people were trying to poison his food.

On this point, "<i>Regarding conspiracy, it's just a fact of life that conspiracies happen</i>", Michael Shermer made the same point in the <a href="https://quillette.com/2019/10/31/the-danger-is-real-why-were-all-wired-for-constructive-conspiracism/">constructive conspiracism</a> post.  

If I remember correctly from the November post, he made a truth table style of argument, saying that believing in a false conspiracy theory is usually harmless, but believing in a true one is helpful, so even though false theories may be more common than true ones, it's still evolutionarily beneficial for people to have a predisposition towards believing them.