Explanation: At the end of the 'Scramble for Africa', a period wherein European powers subjugated and colonized most of Africa, only two states in Africa retained their independence. Liberia, which was an African-American colony, and thus a foreign imposition (albeit of a different sort); and Ethiopia, which was an ancient and native polity which had successfully thrown back invaders for thousands of years.
ETHIOPIA HOURS LET'S GOOOOO
Ethiopia, it must be noted, benefited from both being a relatively stable and coherent polity - with many of Africa's other overthrown powers in the 19th century being relatively recent formations, caused by the chaos of European demand in the slave trade and the introduction of gunpowder by Europeans over the past 200-300 years, and thus less able to resist outside pressure - and from Ethiopia's own natural geography providing a defensible position.