Ancient Egypt specifically fell because of Rome,

It had been conquered by Alexander the great and ruled by Greeks for 300 years before that. And Alexander the great had conquered it from the Persians.

it had a much better time at the early middle ages than a lot of other former roman provinces

It was part of the Roman empire up until the 7th century when it was conquered by the Islamic Caliphate. During the Roman period it was the richest province in the Empire and pretty much funded the whole thing. It was also a personal possession of the Emperor due to its riches.