Well, let's compare the two models.
things round earth can not easily account for:
sometimes one can see things that should be hidden behind curvature
things the flat earth can not account for:
sunsets
motion of stars
existence of maps
ships disappearing behind the horizon
seeing the sunset twice from the top of burj khalifa
the sun and the moon staying (roughly) the same size
mercury/venus transits
eclipses
...
A hughe conspiracy is cool, and one must feel pretty good if one believes to be one of the few awake people in a world of sheep, but this theory can not account for basic daily observations.