When someone creates a fictional lie. Real places and people are mentioned, to give credibility to the lie. The Egyptians kept rather good historical records. They do not mention a Moses, Hebrew slaves, nor them escaping, and nothing about Ramses dying in the Red Sea whilst chasing the escaped Hebrew slaves. The fact is ancient historical records do not agree with the bible at all, and none of the major characters in the bible is mentioned in any other ancient history. The bible is a made up fraud that you are stupid enough to believe in.
From the story, Ramses had Moses name stricken from record. The Egyptians would do that with people, and even would do that with royalty. They also never really mention when they lose in battle. You have to go to the winning side or a third party for real scoop. Besides, would you carve in stone your losses? You know the saying about "History".
What it is, is that it's easier for people to say "it's all a lie", so that in their mind it comforts them.
And it follows the logic that has been going on. First it was "God doesn't exist", then it was "Jesus never existed". Next, "Moses didn't exist", to "it's all a lie".
And what's funny, is that usually each of these is followed by articles that someone had written, or they heard someone say something, and it gathers steam.
Just the same way things happen with mobs. Humans, we think we are smarter than before , but we constantly prove that we are not.