It's a kind of miracle that the Copts have survived so long. But of course all over the Middle East and North Africa the number of Christians continues to diminish. And in Egypt, recurrent massacres of Copts by Muslims are seldom punished. Somehow the perpetrators can never be found.
Actually, a very large number of them were "extinguished" at the point of a sword during the initial Muslim conquests. When Muslims criticize Christians for the crusades, they act as if Palestine and the Levant had been Muslim forever, or as if their conquest in the 7th century was of vacant, empty ground. The fact is that they conquered a Christian population, much of which were slaughtered. The Crusades were a counterattack. According to the Muslims, our aggression was bad, theirs was good -- a double standard.
We see the same double standard at work today. Jews reclaiming the homeland that was theirs long before there ever were any "Palestinians" are evil Zionist aggressors. Yet, if the Muslim world was to have its way (and make no mistake, almost ALL Muslims would approve of this), every single Israeli man, woman, and child would be driven into the sea and have their throats slit. And such Muslim aggression would be perfectly justifiable by their double standard.
We are seeing the same thing even now. The slaughter of over six thousand "infidels" is cause for rejoicing in the streets, while incredibly accurate precision bombing of the most carefully selected and limited set of military targets brings them out in the streets rioting.
All of North Africa was Pagan at the time of the early Roman Empire.
It's not just Islam that eradicates older religions; it seems to be a besetting vice of monotheism in general.