Crank magnetism is the tendency of “cranks” to hold multiple irrational, unsupported, or ludicrous beliefs that are often unrelated. Crank magnetism also denotes the tendency of these people to accumulate more of such beliefs over time.
Those who believe flat Earth will tend to believe other “crank” ideas. Some of these ideas are necessary to support the belief in a flat Earth, like the hoax that moon landings did not happen. But most of these beliefs are not related to flat-Earth.