FYI for everyone: A bad flu year is 60,000 deaths. An average one is 35,000. 360,000 deaths is not a bad flu year by a long shot.
And we can actually detect and distinguish between influenza and covid-19.
So the thing is nobody is rational. "Rational" people are at best people who have as psrt of their self image that they are rational, so feel discomfort when confronted with rational arguments that disagree with their behaviours or beliefs.
But really, people are a near random collection of habits and beliefs. And irrational habits or beliefs? They don't really harm you that much. You don't end up dead very often from believing false things; so long as you mosey along and mostly do things that other people around you do (plus a bit of random crap), you'll do fine, ish.
Thing is, deciding what to do "rationally" is insanely hard. Nobody is actually smart enough to do it. And even people who think they are rational? They can be hacked with "rational" arguments that lead to false conclusions. Being "rational" can make you a mark, because you just exposed your OODA loop.
What more, as luck (of birth, skills, or habits) tends to matter much more than "rational" does, it doesn't even correlate with
power.
The bigest sanction 90/100 people will get from being a flat earther is a social one. Hell, it would only be marginally harder to learn how to fly a plane as a true flat earther believer; just compartamentalize the job from your beliefs.
So you got this bundle of random behaviour, and people actively hacking you with belief systems that make you feel good and make you a mark for the next one.