Yes, the Mediterranean was a big Roman lake and the Roman Empire made the spread of Christianity possible.
-- however, 1400 years of slow genocide has decimated them to now where only 2% of Egypt, 10% of Syria, 2% of the Palestinians, 5% of Iraqis and 45% of Lebanese are Christians.
North Africa and the Middle East are a mixture of many races and cultures. The vast majority of Jews and Arabs never converted to Christianity. And those who did could easily convert to Islam. If Christian roots had been deep in the Arabian peninsula, Muhammad would never have been successful in his jihad.
Yes, I think we do disagree as to why Islam was able to uproot Christianity in the Middle East. And what little is left will continue to shrink.