I understand that the native Christians weren't too upset about not being part of the Byzantine Empire but is their evidence that they actively resisted the Arabs & Muslims? How did they view the Crusades? Were the Christians still in a majority by this point?
This is my first answer in this sub so I hope the quality is up to standard.
So it of course hard to give an exact date of when Christian become a minority in Egypt. The Arab conquest of Egypt was complete in 647, and I think is safe to say that it took about 200 years for Muslims to be the majority. So sometime in the 9th century Egypt become majority Muslim.
You are probably right when you that local Christian were not too upset. Most Egyptian were Monophysite Christians who rejected the Council of Chalcedon and their belief were considered heretical and illegal by the Byzantine government.
Initially the Arabs (a very small minority at the time) separated themselves from the Coptic Egyptians and allowed Egyptians to manage their own affairs and practice their form of Christianity without any interference. But they were required to pay a head tax (in addition to regular land tax). The tax collection was actually done by Coptic Egyptians, so there a good chance that many people never interacted with Arabs at all. During this initial period there were few conversions because there were very Muslims in Egypt and there was no incentive of any kind to push people towards conversion. And odds are people who converted would have been cut off from their community. There is even some evidence that Arabs discouraged new converts because they wanted to guard their own privileged status.
In the 730’s Arabs settlers started to arrive in Egypt from Arabia. These settlers included members from all aspects of society (rich, poor, merchant, laborers etc….) and changed the nature of the Arab population (which was made mostly of soldiers and nobles). These new settlers lived among the Coptic Egyptians but were given higher social status because of their religion. At this point intermarriage started to happen and this further increased the number of Muslims. Coptic men had to convert in order to marry a Muslim girl and a Muslim man married a Copt girl the children were automatically Muslims. Arabic was made the only legitimate language for the administration in 706 and as Arabic spread it blurred the difference between Arab and Egyptian. This further made it easier for people to convert and fit in with the new religion.
During the late 700s and early 800’s there were several Coptic revolts (although Arabs also joined these uprising) due to high taxation and mismanagement. In 832 the Abbasid Caliph Al-Ma'mun violently put down one of these revolts and after this we see the first reference to Muslims being a majority in Egypt. Overall it becomes clear through the 800’s that Egypt is majority Sunni Muslim but with a sizable Coptic minority.
For the next few hundred years the Coptic community would either be treated well or persecuted depending on the political situation. For example when the Shia Fatimid dynasty took over Sunni majority Egypt in 969 they treated Coptic Egyptian very harshly. But later promoted many Coptic Egyptians in into position of power because they posed less of threat to the Shia ruling class than the Sunni majority.
The Ayyubids initially persecuted Coptic Christians but relaxed their stance in 1190’s mainly because they had scored major victories against Crusader states and felt secure in their rule. The Mamluks were by far the most oppressive of Coptic Christians. In 1299 they shut down all churches but this was reversed later. By the 14th century the numbers of Christians is reduced to about 10% of the population (same as today).