Just admit it: because Flat Earthers cannot grasp the complex mathematics behind rotating three dimensional spheres they've made it flat.
Flatters aren't necessarily bad at math, they are AFRAID of math.
Math proves they are delusional. Math proves they are wrong.
Take AltSkepti/R2dc3po for instance, he even flees his own thread when faced with doing the math for satellite directions and elevations.
Same with distances between cities.
They are afraid of doing the math, they know it proves them wrong.