Point of Divergence
Main article: Fifth Crusade (Many Wonderful Things)The Fifth Crusade in the early 13th century was the farthest Europeans had penetrated into the land of Egypt since the arrival of Islam. At the time the port city of Damietta was taken in November of 1219, the crusaders in Egypt were led by the Papal legate Pelagius Galvini. After the battle was over, the French nobleman John Brienne arrived and claimed supremacy over the forces in the city. In our timeline, these two individuals continued to dispute until the Crusade ended in 1221.
In this alternate timeline, Galvini allows Brienne to hold the city, allowing the crusaders under Galvini to press farther along the delta and ultimately march on Alexandria. In the process of doing so, they would encamp in various smaller towns including the city of Rosetta, which at this time would be known by its Arabic name of Rashida. Thus, it is at this time that the Rosetta stone (known in this timeline as the Tabula Rashida) is accidentally discovered by the crusaders and sent back to the Papal States by Galvini.
In the hands of the monastic scholars of 13th century Italy, the tablet is used to break through the language of hieroglyphics, and ultimately led to a flourishing of archaeological enthusiasm as it did in OTL 19th century.
Changes to History After the Divergence
See Also: Aegyptography (Many Wonderful Things)The most immediate affect of this divergence is an increased understanding and interest in Egyptian history during the late Middle Ages. Obviously, this ATL Egyptology would not grow as quickly as in OTL for multiple reasons, such as less access to Egypt and less technology for archaeology, but over time the history and literature of the nation would be revealed. It certainly helps that the Muslim dynasties of Egypt considered all of their artifacts as worthless pagan relics, and would therefore be more willing to sell them to Europeans who consider them more valuable. It also helps that many Egyptian artifacts that were lost in our timeline would still exist in the Middle Ages. By the height of the Renaissance in the 15th-16th centuries, at least all of the Egyptian history known OTL would be uncovered and translated to one degree or another.
The availability of Ancient Egyptian science and technology in the Renaissance would make as much impact as Greco-Roman literature did OTL. The secrets of the Pyramids and Obelisks would be incorporated into these monumental architecture. The technology of canal building would ultimately help in the construction of the Suez Canal. In terms of biology, certain extinct species of plants preserved in Egyptian tombs may be released into Europe during this time.
The greatest political change would not be felt until the late 18th century, at the time of Napoleon's campaign that coincidentally discovered the stone OTL. But instead of questioning the origin of the Pyramids in vain, Napoleon would have complete access to the history of Egypt back in Corsica, and may even add this knowledge to his great dossier of mathematics and history. In fact, if Napoleon utilized the tactics of the Egyptian Napoleon, Thutmose III, he may have reenacted a similar successful campaign to take all of the Levant as far as Syria.
He would ultimately be defeated as before, but in the process give over a larger territory to the British protectorate of Egypt. The British control of this area in the 19th century eventually leads to the state of Palestine gaining independence around the turn of the century, about the time of the second Jewish Aliyah. This in turn leads to a very different case for Palestine's conflict with Egypt.
Additionally, there are other organizations who depended on the fact that hieroglyphics could not be translated OTL. These people include the Illuminati, the Mormons, and the Coptic Church. At the same time, other cult religions would form in their place as the religions of Ancient Egypt are better understood.
Changes to History Before the Divergence
Main Article: Ancient Egyptian Chronology (Many Wonderful Things)Instead of the ivory-tower intellectuals of the 19th century, Egyptian history in this timeline is first constructed by the Scholastic monks of the 13th century, perhaps even such brilliant minds as St. Thomas Aquinas. Because of this, the history of Egypt would be interpreted very differently, as these thinkers would conform their discoveries to the Judean-Christian presuppositions of ancient history.
For instance, the beginning of Egyptian history would have to placed after the Tower of Babel in the 23rd century BC, with some subsequent dynasties merged of overlapped to accommodate this restraint. Similar alterations are used to match later Egyptian history with other Biblical and classical events, from the Exodus to the Dannaids. The interpretation of these presuppositions may be debated and altered, but some synthesized history would be concluded even before world history is invented by Sir Isaac Newton and Joseph Scaliger in the 17th century.
In general, Egyptian chronology would be laid out within the Seven Ages of Man accepted in the Middle Ages: The First Age until 23rd cen. BC (Predynastic), Second Age 23rd-20th cen. BC (Old Kingdom), Third Age 20th-16th cen. BC (Middle Kingdom), Fourth Age 16th-11th cen. BC (New Kingdom), Fifth Age 11th-6th cen. BC (Late Kingdom), Sixth Age 6th-1st cen. BC (Persian and Ptolemaic Dynasties), and finally the Seventh Age encompassing the Middle Ages.