Summary: The concentration of power and economic activity with automation can be self-defeating.
The government became paranoid of all sources of illicit goods, so they utterly restricted the first nano-fabbers. Even still, their restrictions did little to deal with the corruption, gangs, and pollution that plagued the average citizens of the era. Ignoring the reality outside, the oligarchs' restrictions became much ever draconian.
The country collapsed into expanses of ravaged wilderness, interspersed with the estates of neofeudal gentry. Cities collapsed into sprawling slums with pockets of fortified penthouses. Where the two met, only pollution bloomed. As robotic security became more common, state officials rarely ventured forth without their own killer robots. Each was run by proprietary bloatware, as their owners scorned open source alternatives.
Each death-bot was equipped with a variety of progressively more powerful weapons, to be deployed if a trespasser did not obey. Patrols of security-bots kept order in the slums, despite the ease with which they were tricked or hacked. The ones that guarded the kleptocrats were far more sophisticated, deadlier, and smarter than the mercenaries they replaced. Their businesses were managed by automated investment software, similarly smarter than their human counterparts.
When two oligarchs toured a slum, their mechanical entourage sent the locals scurrying like rodents. A drunken dispute between the two escalated to a shoving match, and their servitors formed a phalanx between them. It collapsed into a firefight a second later, leaving only a pair of robots blasting everything that moved.
An old woman with a homemade shotgun that put the slaughterbots out of commission, putting them down like rabid animals. The bodies of the oligarchs were dumped into a different neighborhood, so the security patrols would focus on the drug-gangs instead of their own food gardens. All of the slum-dwellers' actions were technically legal, as they consulted an open source legal advisor. After their deaths, business algorithms managed the estates far more efficiently than either of the oligarchs ever did.