Flying triangles of the large hovering type are nothing more then experimental aircraft. They use standard technology, one might call it anti-gravity, but it really related more to buoyancy and hot air balloons. I am not the first to think of this either, came to me right after my gravity theory, and there are U.S. Patents on it.
The secret is that no air or a vacuum is lighter versus hot air. Instead of a flexible bag, one would need to make a light rigid shape or hull. Triangles are naturally strong shapes to build with and are commonly used in buildings, cars, etc. A tough membrane could be stretched over a tube frame to make the cavity. There could be multiple layers to reduce catastrophic loss of vacuum. Depending on the amount of leakage, a large vacuum pump is not needed to maintain an acceptable level of vacuum. The larger the airship becomes the more efficient the design becomes. The efficiency is determined by the surface to volume ratio (same idea as my gravity theory almost, but backwards due to the inverse nature of energy versus matter compared to our perspective, E=mc squared after all), which would still depend on the weight of the support structure and membrane. A round shape would be the most efficient at lifting. However, it is not the ideal shape for moving through the air efficiently. The triangle is a good compromise. It is an airboat.
This same method can be used to lift any size or weight and in my opinion was used by ancient man to lift the mega sized blocks. The only difference is the medium, water versus air. Romans used hydraulic mining to change (destroy) valleys in the search for gold. If a load will float and is in a small pool, adding water to the pool will lift the load as long as the pool does not leak, it is magic. Add a closeable wall at one end like a ship lock and you can lift and move large loads very easily. We still use boats and the water for the same reason, the efficiency of moving large heavy loads. Is it so hard to imagine the ancient Egyptians making a staircase or spiral canal up the side of the pyramids and using water to move and lift those mega-sized stones? There must have been a reason to make the walls as high as they were for the rampway from the Nile that is in some descriptions. In my opinion, it was to hold water and float loads so they did not have to drag them all. A chain gang of women and children could keep the pool at the top full or using ancient water lifting machines used in Iraq. Fine grit (sugar) sand will hold water quite well as long as undisturbed.
Religion is one of the very few things that really survives a collapse of humanity, or a large reduction in population. Everyone knows pieces of knowledge, but few know enough to do anything useful after a collapse. Like the one long ago in which only a handful of groups survived in and around Africa. Humans were not the only ones that were affected either. It was a global change.