Oh, there's population pressures and land depletion issues also; the old days when a tribe could move into new territory, and herders find fresh pastures, and loners could forage in the wild, conferred a bit of safety that city-bound populations don't have.
Blaming 'bad politics' might be a cheap shot; which is the cause, and which the effect? Economics of limited resources are subject to Malthusian logic. Politics is always involved, but so is gravity, and air, by the simple mechanism of ubiquity in human life.