Answer:
It is hard to give only one cause to such a big historical event. The decay of empires can be a long duration event with a dozen of causes. However in this case it is safe to say that this set of events has one common fundamental cause: transatlantic slave trade.
Explanation:
The transatlantic slave trade was a long duration event that completely changed internal dynamics of African empires. Although to say that it destroyed Africa's cultural achievements is too much, it certainly impacted the entire continent.
Africa had internal slave trade since long time before the 14th century. This trade however was small and connected with demands internal to states in the continent. When the atlantic trade started and became routine it was big business, the bigger of the modern era: it was a world trade that was responsible for much of the growing of many entire nations.
The last country to abolish slavery was Brazil in 1888. Transatlantic slave trade started in the 1400s with technological developments that improved navegation and ended in mid 1800s.
The Paris Peace Conference convened in January 1919 at Versailles just outside Paris. The conference was called to establish the terms of the peace after World War I.
Civil War killed off slavery and declined the southern economy it also acted as a catalyst to make America into a complex industrial society of capital, technology, national organizations, and large corporations.
It created new jobs and it expanded industries
