But how would it seize power?
The Fatimids were in a somewhat sorry state on the eve of the crusades... Maybe if the crusades never occur, or if Salah-ad-Din establishes the Ayyubid power base out of Syria, a native warlord could rebel against them.
But how would it seize power?
I think generating a few native dynasties, rather than Egypt constantly being ruled by Arabs/Turks/Circassians/Albanians might be a nudge in the right direction, post Islamic conquest.
After all, a native dynasty, however it seizes power, will have to do something to legitimate itself. I'd say descent from the builders of the local pyramids - paganism notwithstanding - would help that.
But how would it seize power?
A powerful native born convert noble takes power in some kind of civil war, the pre crusade Fatmids where at their absolute weakest and if a native managed taking it it he could probably have held onto power.