Would you want the world to know that your government was intimidated and pillaged by an uprising of slaves, shepherds too! This is an embarrassment to the Egyptian people, the most powerful nation around.
Egyptian historical records were meant to glorify the existing powers showing future generations how great they were. They would do everything possible to leave this off the history books.
The story of Moses, the plagues, the exodus and the defeat of the Egyptian army at the Red Sea point to God’s power, not the Egyptian gods’ power. Since Pharaoh thought he possess divine abilities, it lessened his legacy.