https://youtu.be/omajagaozk0 After watching these videos im mesmerized by how well their society was set up and looked. What happened to the Egyptians? How did they die off when they were so well set up?
I've answered a question like this before. The idea of a culture or civilization just dying out is actually a pretty rare one in history. More often they are just subject to extensive outside influence, as I described for Egypt in the linked thread.
If you want a really detailed look at the decline of the unique "Ancient Egyptian" culture I recommend The Twilight of Ancient Egypt: 1st Millennium B.C. by Karol Mysliwiec, trans. David Lorton