Egypt, Syria, Palestine, Iraq and Iran were primarily agricultural societies. The landscape of these places was typical of farming societies: small towns scattered among farms. By the 7th century, they were mostly Christian, though not all Catholic or Orthodox. The Armenians and Nestorians had their own churches, perhaps based in very early conversions centuries earlier.
When the first Companions of Mohammed conquered the Holy Land, their chief concern was to keep their own tribesmen from rebelling. They encouraged the tribes to migrate freely into the conquered lands and take what they wanted, as a way of pacifying them. Their early legal precedents were few, mostly based in whatever Mohammed had done in particular situations. Taxes were very high, and they took not just cash-based taxes but many provisions and goods of all kinds. The conquered people were property; the Arab tribes received stipends out of the revenue, in addition to migrating into the land.
There was a basic legal precedent from the beginning that the oath of a non-Muslim in court was worthless against the word of a Muslim. No Muslim could be condemned to death for murder or theft on the word of a non-Muslim, either. Muslims could take land, animals, and other property without any penalty. At sea, they could hold anyone for ransom. The only way that a non-Muslim could get justice was to pay heavy bribes to judges. The judges, of course, used the income to increase their own power.
At the time of conquest, half of the churches had been ceded as mosques. As the Christian inhabitants grew poorer or went into hiding, most of the other churches were abandoned or seized. Egyptian and Syrian monasteries were abandoned.
In the early years, taxes were often so crushing that native Syrian, Egyptian and Nestorian farmers abandoned their land and went into hiding. They hid in the hills and caves. In some cases, Bedouins moved in with flocks and grazed on the land.
Gradually, the landscape began to change; if you’ve ever seen goats at work, you’ll know what I mean. The plants that they like are soon gone, and the plants they don’t like are the only ones that grow. Desertification resulted (we don’t often stop to think that perhaps the landscape we see around flocks of goats was created by the goats themselves). By 700 or so, tax revenue had massively fallen. Some of the same changes happened in Spain, too, as a result of the Berber-backed conquest. Nomads were poor stewards of land.
The Muslim governors of these provinces tried to reverse the Arabization by evicting nomads and hunting down the original farmers, forcing them back to their fields. They began to see a need to give the natives some legal protection, so at least they tied some taxes to the land, not just to the people. But there had been a real reason to pay off the Bedouins with such privileges. As the Umayyad Caliphs began to set things into better balance, reducing nomad stipends and restricting immigration, the original Arab tribes gathered energy to rebel. By no longer favoring the nomads and trying to restore agriculture, the Umayyads brought their dynasty to an end.