This is a question that many people have asked again and again over the ages and generations. Identical twins have remained a subject of awe and amazement.
We have a very detailed article here that will give you the full gist, why identical twins do not share identical intelligence levels.
You can view it here https://natureloaded.com/factors-influencing-intelligence-levels-among-identical-twins/
You may also like to see our other article on the Mystery of Identical twins here