Language proximity cannot explain why Iran avoided Arabization

Evidence

One suggestion is that the difference is language. The peoples of Iraq, Syria, Palestine, spoke various forms of Aramaic. Aramaic is a Semitic language related to Arabic, and the transition from Aramaic to Arabic was much easier than would have been the transition from Persian, an Indo-European language, to Arabic. There is some force in that argument. But then Coptic, the language of Egypt, was not a Semitic language either, yet this did not impede the Arabization of Egypt. Coptic survived for a while among the Christians, but eventually died even among them, except as a liturgical language used in the rituals of the Coptic Church. — Bernard Lewis, From Babel to Dragomans, 280

Categorization

• QUESTION: So if not language or superior culture, what actually explains Iran’s survival? Lewis cuts the two standard answers but doesn’t yet offer his own — worth tracking where the argument goes.
• corroborated: 2 independent passages support this claim — Bernard Lewis, From Babel to Dragomans: Interpreting…, 280