190) “Cultures the world over throughout history have all described and purported the existence of a geocentric, stationary flat Earth. Egyptians, Indians, Mayans, Chinese, Native Americans and literally every ancient civilization on Earth had a geocentric flat-Earth cosmology. Before Pythagoras, the idea of a spinning ball-Earth was non-existent and even after Pythagoras it remained an obscure minority view until 2000 years later when Copernicus began reviving the heliocentric theory.”

It is not true that flat-earthism was dominant until the time of Copernicus. or that it was "an obscure minority view" that the earth was spherical after Pythagoras.  If it had been, we would have a historical record of many objections to heliocentrism on flat-earth grounds, and we don't.

"So, for the last 2500 years, in Europe and in the Middle East, the flat-earthers were in a very small minority. At least, this is what the historian Jeffrey Burton Russell, of the University of California at Santa Barbara, reckons.

His book, In Inventing the Flat Earth, claims that since the third century BC, practically all educated people in the western world believed in a spherical earth.

Looking as a historian into the historical record, he found tens of thousands of Christian theologians, poets, artists and scientists who believed that the earth was a sphere.

On the other hand, he could find only five Christian authorities who believed in a flat earth.
Dr Russell wrote:

In fact, Burton found that the myth was started in the 1830s by a Frenchman and an American, acting independently.

The Frenchman was Antoine-Jean Letronne (1787–1848), an antireligious academic of great renown. He wroteOn the Cosmographical Ideas of the Church Fathers in 1834.

He deliberately misrepresented medieval Christians as being scientifically ignorant, and his supposed proof for this incorrect claim was that they believed in a flat earth. But of course they did not believe in a flat earth.
The American identified by Burton was Washington Irving (1783–1859), who wrote his history of Christopher Columbus in 1828. Columbus wanted to sail west to China, Japan and India.

Irving painted a colourful and dramatic word picture of Columbus trying to convince a board of flat-earther inquisitors (the Council of Salamanca) that the earth was round, so that he could get funding.

Like all good myths, there is an element of truth here. Columbus did meet with a board of scientists. The scientists claimed that Columbus' distances for getting to the east by sailing west were wildly wrong — actually 20,000 nautical miles, rather than the 5000 claimed by Columbus."
"In the first fifteen centuries of the Christian era, five writers seem to have denied the globe, and a few others were ambiguous or uninterested in the question. But nearly unanimous scholarly opinion pronounced the earth spherical, and by the fifteenth century all doubt had disappeared."

http://www.abc.net.au/science/articles/2009/07/22/2633359.htm

You will find a reasonable summary of the false nature of claims that flat earth belief was widespread in Myth of the flat Earth at https://en.wikipedia.org/wiki/Myth_of_the_flat_Earth

And at https://en.wikipedia.org/wiki/Spherical_Earth

"Late AntiquityKnowledge of the spherical shape of the Earth was received in scholarship of Late Antiquity as a matter of course, in both Neoplatonism and Early Christianity. Calcidius's fourth-century Latin commentary on and translation of Plato'sTimaeus, which was one of the few examples of Greek scientific thought that was known in the Early Middle Ages, discussed Hipparchus's use of the geometrical circumstances of eclipses to compute the relative diameters of the Sun, Earth, and Moon.[30][31]

Theological doubt informed by the flat Earth model implied in the Hebrew Bible inspired some early Christian scholars such as Lactantius, John Chrysostom and Athanasius of Alexandria, but this remained an eccentric current. Learned Christian authors such as Basil of Caesarea, Ambrose and Augustine of Hippo were clearly aware of the sphericity of the Earth. "Flat Earthism" lingered longest in Syriac Christianity, which tradition laid greater importance on a literalist interpretation of the Old Testament. 

Authors from that tradition, such as Cosmas Indicopleustes, presented the Earth as flat as late as in the 6th century. This last remnant of the ancient model of the cosmos disappeared during the 7th century. From the 8th century and the beginning medieval period, "no cosmographer worthy of note has called into question the sphericity of the Earth."[32]

IndiaWith the spread of Greek culture in the east, Hellenistic astronomy filtered eastwards to ancient India where its profound influence became apparent in the early centuries AD.[33] The Greek concept of an Earth surrounded by the spheres of the planets and that of the fixed stars, vehemently supported by stronomers like Varahamihir and Brahmagupta, strengthened the astronomical principles. Some ideas were found possible to preserve, although in altered form.[33][34]

The works of the classical Indian astronomer and mathematician, Aryabhatta (476–550 AD), deal with the sphericity of the Earth and the motion of the planets. The final two parts of his Sanskrit magnum opus, the Aryabhatiya, which were named the Kalakriya ("reckoning of time") and the Gol ("sphere"), state that the Earth is spherical and that its circumference is 4,967 yojanas. In modern units this is 39,968 km (24,835 mi), close to the current equatorial value of 40,075 km (24,901 mi).[35][36] 

Middle AgesKnowledge of the sphericity of the Earth survived into the medieval corpus of knowledge by direct transmission of the texts of Greek antiquity (Aristotle), and via authors such as Isidore of Seville and Beda Venerabilis. It became increasingly traceable with the rise of scholasticism and medieval learning.[25] Spread of this knowledge beyond the immediate sphere of Greco-Roman scholarship was necessarily gradual, associated with the pace of Christianisation of Europe. For example, the first evidence of knowledge of the spherical shape of the Earth in Scandinavia is a 12th-century Old Icelandic translation of Elucidarius.[37] 

A non-exhaustive list of more than a hundred Latin and vernacular writers from Late Antiquity and the Middle Ages who were aware that the earth was spherical, has been compiled by Reinhard Krüger, professor for Romance literature at the University of Stuttgart.[25]

Late Antiquity Ampelius, Chalcidius, Macrobius, Martianus Capella, Basil of Caesarea, Ambrose of Milan, Aurelius Augustinus, Paulus Orosius, Jordanes, Cassiodorus, Boethius, Visigoth king Sisebut. Early Middle Ages Isidore of Seville, Beda Venerabilis, Theodulf of Orléans, Vergilius of Salzburg, Irish monk Dicuil, Rabanus Maurus, King Alfred of England, Remigius of Auxerre, Johannes Scotus Eriugena, Leo of Naples (German), Gerbert d’Aurillac (Pope Sylvester II). High Middle Ages Notker the German of Sankt-Gallen, Hermann of Reichenau, Hildegard von Bingen, Petrus Abaelardus, Honorius Augustodunensis, Gautier de Metz, Adam of Bremen, Albertus Magnus, Thomas Aquinas, Berthold of Regensburg,Guillaume de Conches, Philippe de Thaon (French), Abu-Idrisi, Bernardus Silvestris, Petrus Comestor, Thierry de Chartres, Gautier de Châtillon, Alexander Neckam, Alain de Lille, Averroes, Snorri Sturluson, Moshe ben Maimon, Lambert of Saint-Omer, Gervasius of Tilbury, Robert Grosseteste, Johannes de Sacrobosco, Thomas de Cantimpré, Peire de Corbian, Vincent de Beauvais, Robertus Anglicus, Juan Gil de Zámora (Spanish), Ristoro d'Arezzo, Roger Bacon, Jean de Meung, Brunetto Latini, Alfonso X of Castile. Late Middle Ages Marco Polo, Dante Alighieri, Meister Eckhart, Enea Silvio Piccolomini (Pope Pius II), Perot de Garbalei (divisiones mundi), Cecco d'Ascoli, Fazio degli Uberti (Italian), Levi ben Gershon, Konrad of Megenberg, Nicole Oresme, Petrus Aliacensis, Alfonso de la Torre (German), Toscanelli, Brochard the German (German), Jean de Mandeville, Christine de Pizan, Geoffrey Chaucer, William Caxton, Martin Behaim, Christopher Columbus."

https://en.wikipedia.org/wiki/Spherical_Earth