Sokarul,
I'm afraid I must disagree with you on one point. When people pull theories "out of their asses" as you put it, those theories do not "all fail".
Democritus, a pre-Socratic philosopher, posited the existence of something he called the "atomon" or "indivisible unit". These "atoma", he believed were too small to see and made up all the objects of the universe by their various arrangements. These had very few qualities one could discern, but by arranging in different ways they made the multitude of the various forms of matter we observe: "By convention sweet, by convention bitter, by convention hot, by convention cold, by convention colour: but in reality atoms and void."
This was not discovered with a microscope, mind you. Nor was it intuitively obvious (the idea was discounted by Aristotle who believed that "nature abhors a vacuum"). Indeed this was simply "pulled out of [Democritus'] ass" (the ass of Leucippus also deserves some credit).
As was his belief that the lights we see in the night sky from Earth are coming from distant stars (some of which he postulated might be inhabited).
I'm not saying Democritus got everything right (he believed, for example, that atoms could not be divided), but I wouldn't say he, or his theories failed.
But to address your intended point at long last, yes, it does seem difficult to imagine how so many people would miss something so fundamental (if the Earth were flat). But I do present scenarios in the other forum topic (which I'd be happy to repost here) that make it logically consistent, even if it is improbable.