Try /r/AcademicBiblical for some specialists.^1
^1 Reference: /r/AcademicBiblical.^2
^2 I'm not sure i have the hang of this reference thing.
Because the story of Exodus was written a long time after the fall of the Assyrians and thus was composed of history from an oral tradition that had changed over time (we assume this because the archaeology and linguistics don't match up with the bible).
You might as well ask why the story of Moses and the story of Cyrus the Great have so many similarities.