Why did the Egyptians build tombs in the shapes of pyramids?

im not positive but i think one pharaoh wanted a grander tomb.

Also, if this helps, i know that before the pyramids egyptians used mastabas, a rectangular tomb to bury the pharaohs. The pharaoh had egyptians hand cut all the bricks out of the ground for the pyramids, and they were big. I think it took three years to build the first pyramid.

hope it helps