But yet by the 6th century, Egypt was Christian for 300+ years. In fact, it was arguably the centre of Christian thought. So why that period for the pyramids to be boarded?
Christians were officially persecuted in the Roman Empire until the 4th c, and there was at least one pagan revival after Constantine. The shift from paganism to Christianity wasn’t yet complete when Mohammed emerged with his largely plagiarized screed and his mass-murdering pedophilic ways.