I don't know of any instances where entire civilizations were overthrown by internal populations, but the first thing that comes to mind insofar as "abandonment of mass society and urbanism" goes is the European colonists escaping the plights and misery of the first expeditions and colonial townships to live with the indigenous Americans. But that doesn't necessarily mean they weren't confronted with urbanism and whatnot. (Regardless, I'm sure they were much better off. I'm not really sure "mass society" existed prior to the advent of industrial-based economies and—let's say: mass communications technologies? I only have a very broad idea of what "mass society" means informed by my own bias.)
I'm not so much answering your question as poking around with curiosity. But, yeah, the colonists jumping ship immediately comes to mind.