WHEN EMPIRES COLLAPSE (2 at the least, 4 at the most, occurs simultaneously):
(a) Disease Pandemic, Disease Outbreak
(b) War, Revolution, Rebellion, Independence Movements Emerge, Suppression
(c) Economic Collapse
(d) "Climate Change" and Natural Disasters (ex: drought, famine)
Because trade routes are disrupted, business is halted, food becomes scarce, mass emigration occurs, money becomes worthless, jobs are scarce and hard to find.
New identities are formed, New lifestyles are created, New myths and narratives are created, New Gods and belief systems/ideologies are implemented, New forms of governments and New rulers take over, and the "old world" becomes nothing more than a faded memory, which some of the living will romanticize and others will want to forget in order to rebuild their lives and move on.