If there are only 0.1% of flat earthers, why would 10% of people think it to be the most popular answer? That does not seem realistic at all.
Or did you interpret the question as suggested by bena in his sibling answer, ie as an estimate for the answer distribution (that would then have to be averaged) instead of a choice of the most popular answer (as was done in the wiki article)?
That does seem realistic considering how often the topic pf flat-earthers comes up in discussions on social media, despite it being an extremely niche view.
OP suggested that 10% of people think there are more than 50% of flat-earthers when the real number is 0.1%. Phrased another way, 10% of people expect half the people they meet will be flat-earthers when it's 1 in 1000.
Or did you interpret the question as suggested by bena in his sibling answer, ie as an estimate for the answer distribution (that would then have to be averaged) instead of a choice of the most popular answer (as was done in the wiki article)?