The Copts were also there before there was such a thing as Islam.
I have also read that the Coptic Church, which is still monophysite (i.e., believing Christ only had one, divine nature,) adopted the monophysite heresy as a kind of nationalism in opposition to the Greek ruling class in Roman Egypt, which was orthodox Christian. I don't know if the evidence supports this view -- it could be 19th- and 20th-century scholars imposing their modes of thought on past evebts.