Did the men who sailed with Columbus believe the earth was flat?

No, the men who sailed with Columbus did not believe the Earth was flat. By the late 15th century, educated Europeans widely accepted that the Earth was round, a fact known since ancient Greek times. Columbus himself argued for a shorter route to Asia based on a spherical Earth, although he underestimated the size of the planet. The misconception that people in Columbus's time thought the Earth was flat is largely a myth popularized in later centuries.