Finkle,
I think they were displaced nomads that took over some cities to have a more permanent residence. The coming out of Egypt scenario an attempt make a good story telling device that that satisfied those that held the power and the priesthood that makes a living out of telling these stories. Like Yahwey would really care if someone picked up sticks on a Saturday and have Moses tell the people to execute the violator of a god decreed rest day.
https://en.wikipedia.org/wiki/Nomad
The first nomadic pastoral society developed in the period from 8,500–6,500 BC in the area of the southern Levant.[citation needed] There, during a period of increasing aridity, Pre-Pottery Neolithic B (PPNB) cultures in the Sinai were replaced by a nomadic, pastoral pottery-using culture, which seems to have been a cultural fusion between a newly arrived Mesolithic people from Egypt (the Harifian culture), adopting their nomadic hunting lifestyle to the raising of stock.[8]
This lifestyle quickly developed into what Jaris Yurins has called the circum-Arabian nomadic pastoral techno-complex and is possibly associated with the appearance of Semitic languages in the region of the Ancient Near East. The rapid spread of such nomadic pastoralism was typical of such later developments as of the Yamnaya culture of the horse and cattle nomads of the Eurasian steppe, or of the Mongol spread of the later Middle Ages.[8]