Again, there was more than 2,000 years between those simple nomads and the pyramids. Even cattle herder populations grow over time.
Where did the surplus food come from to feed the army of workers?
Farming appeared at some point, in the Nile valley, and probably early. Farmers in the Nile valley grew tremendously large crops without the benefit of technology. With the regular flooding of the Nile River they didn't need it. You have to have a well organized state to produce the surplus needed to feed work crews.
Egypt had a very well organized state, even before the first dynasty. People do not invent writing, as the Egyptians did, without great organization and beauracracy, apparently.
Watch the news. Those regions of the world have hardly evolved over the centuries. You still have nomads and cattle herders roaming thru the desert etc. They haven't changed. Can you imagine these people creating the culture needed to build pyramids?
Don't just watch television. Read a book. Read some history. Those regions led the world in many ways until the 15th century. I could go on and on about the basic technology that was invented in "those regions".
Trigonometry and geometry, for example, were invented in the middle east. The greeks and romans got it from them. A temple school has been dug up in Babylon. There were clay tablets there which appeared to be work books for geometry students.
Two thousand year old jewelry has been found that appears to have been electro-plated with gold. You need electricity for that. Well, it appears that primitive electric batteries have been found in Babylon that would have done the job.
Nomads? Shoot, there are nomads in the USA. Yes, I can imagine that these people created a culture capable of building the pyramids, and much else besides. I don't have your low opinion of people. People all over the world have built tremendous structures, and none of them needed space aliens or Atlantis to do it.