So the statement that it wasn't about the fall of Christianity makes little sense, as Paganism, not Christianity was the religion of the Roman empire (Western Empire, as the author says) for almost its entire existence.
The fall of Rome was contemporanius with the widespread failure of Hellenic Paganism, and the gradual transition of the Empire towards Christianity.
Constantine's conversion and reign led directly to the founding of Constantanople, and the shift in the center of power to the east. Still, Constantine's adoption of Christianity didn't bring a complete end to Paganism, and his nephew who followed him as emperor, Julian (or Julian the Apostate if you prefer the Catholic label for him) attempted to revive the flagging faith.
So, maybe what's happening is that the moon-cult is dying, and Arab civilization along with it. I've been struck watching the Egyptian protests how few people seem to have any religious ferver. Prayer time comes and 14 people start doing the Moslem Calisthenics, but there are 20 people in background talking on cell phones and wandering around waiting for it to be over so they can get back to what they were doing.
Paganism was the official religion of Rome for the vast expanse of it's history. Towards the end people sort of lost interest in it and what started as a slow slipping away of a few towards Christianity accelerated into a majority over a few hundred years.
If average Egyptians can access twitter to organize a rebellion they can probably also access Wikipedia to read about the life of Mohammed.
I have often thought that Islam can not long survive as a religion once the simple facts about Mohammed's life is available, especially when the contrasting life of Jesus is also available.
There was a very old and revered saying in Rome that as long as the eternal flame, the Sacred Fire of Vesta, in the temple of Vesta, which pre-dated the Republic itself, burned, the city would live. Theodosius I. ordered it extinguished in 394 AD. Rome was sacked, for the first time in it's long history in 410 AD.
Arab Civilization and Islam are completely intertwined, neither can exist without the other, but I suspect that the slow dwindling of Islam will be the leading indicator.
Once Arab civilization falls, the rump-Islam in places like Indonesia and Malaysia will dry up and blow away, just as Paganism did after the fall of the Roman empire in 476 AD.
The Roman Empire made the grave error of granting citizenship to those who were not acting in the interest of Rome.
Sound familiar? History repeats itself, and often with disasterous consequences when ignored.
Rome was sacked by the Gauls in 387 BC. That's why we only have the legends about its founding and no written records from before that year.
In addition, I have read that more and more, people in the ME are not identifying as “Arab” but as Egyptian, Lebanese, and Syrian, emphatically disclaiming their ethnicity as Arabs.