carving limestone blocks the size of mobile homes with copper tools,
Interestingly enough there is a lot of iron ore in Egypt; they used an iron tool in the Opening of the Mouth ceremony for the dead; W Budge also mentions a steel tool used in the same ceremony (Book of the Dead -1887) - this iron is assumed by Hawass & Lehrer to be meteoric iron.
Also any existing iron tools would have been seen as valuable, stolen, sold during any one of the Interregnums between the Kingdoms. Also the Arab muslims in the 7th century would also have stolen anything valuable like iron tools (for making knives and swords) leaving the copper and stone tools behind.
There is also a way to harden copper such that it is harder than steel.
That is not the case.