Amenemhet III was the 6th pharaoh of the 12th dynasty of Egypt. He built 2 pyramids; the Black Pyramid at Dashur and this one at Hawara.
While the pyramids of the Old Kingdom were made of solid limestone blocks, the 12th dynasty (Middle Kingdom) pyramids had a core that was made of bricks (containing mud and straw) and an outer veneer of limestone.
Over the centuries, the outer veneer has fallen down as a result of erosion and earth quakes or stolen by people to be used elsewhere. What remains is the mud brick core which has been eroded further by the weather.
If you look carefully, the straw within the mud bricks is still quite easy to see.
It would have taken an enormous number of slaves to make this number of mud bricks, let a lone assemble them.
It is likely that the mud bricks in these 12th dynasty pyramids were made by Hebrew slaves prior to the Exodus.
Amenemhet III would have been the Pharaoh that Moses fled from.
When the Exodus took place in 1445 BC, there were not enough slaves left in Egypt to make mud bricks and so no more pyramids were built.
The dates do not match with the traditional dates calculated from Manetho because many dynasties and regencies ran in parallel and some dynasties have been counted twice. The Egyptian Chronology needs to be revised and then it will match the Biblical Chronology.