Why didn't the mesopotamian area develop as much in architecture in art as the egyptians?

Answer 1

It depends on how you are defining "develop." The hanging gardens of Babylon were built in Mesopotamia, they were one of the 7 wonders of the ancient world. They probably weren't as monolithic as the pyramids, but were probably more complex architecturally than the pyramids which are essentially just artificial mountains, they're dead structures not meant to be used for any practical day to day purpose. The Hanging Gardens were something royalty would visit and use every day, they had terraces and galleries that were described as "theatre-like" by Greek chroniclers. The Hanging Gardens were destroyed by fire, something that isn't going to happen in a structure 10 people ever enter in their lifetime. Beyond that Egyptian architecture, while monolithic, wasn't technically complex. Things like gypsum mortar, concrete, the arch, domes, were not seen until Hellenistic or Persian influences brought them.