I have two thoughts on this.
1. Pyramids, as a block structure, are quite easy to build. There's some professor in France (I think it was) who has just proved his theory on how the pyramids were really built, and it amazed fellow world associates. (I tried to find a link, but couldn't. Maybe someone else is aware of this guy?)
2. Pyramids are believed to have certain preservative powers, which would be perfect for their dead kings etc. The power is most concentrated at 2/3rds up from the floor of the pyramid. I have actually done tests on this theory back in the '80s for a school project and proved it quite successfully on meats and dairy products. (A funny story - we forgot about the project after the results and found the pyramids still in a cupboard in the science room about 6 months later with the products still present. The products under the pyramid were still in a decent condition whereas the product outside of the pyramid was totally rotted away. FYI, the pyramids I built were only a wood frame, not solid enclosed sides.) There's also the theory that if you wear a pyramid frame as a hat, one can improve brain power. I didn't test that one. Perhaps I should have. I might've passed physics!!