I heard an end times preacher once say that that is because when God begins to do His mighty work in Israel, Egypt will recognize that they’ve been down that road before and repent this time.
If anything shows the patience of God and His desire to see someone come to Him.
I’m becoming convinced that God will never let a person be condemned who might come to Him eventually. IOW, that those who die without Him would never have accepted Him.
In this case, while Israel obliterated many nations around them, Egypt is still here and we see why now. They will eventually turn to Him.
Dr. Arnold Fruchtenbaum (whom I believe is a Jewish convert, might be wrong about that) wrote a nice article on the OT basis for premillenialism.
It is here ...
http://www.pre-trib.org/articles/view/premillennialism-in-old-testament
At the end of the article, he does a pretty good job of explaining what the nations will look like during the MK.