原文：
If you just read up on the history of China between 1900 to 1949, the reasons would be glaringly obvious to you. Basically because China was a shit hole that had tried everything - monarchy, constitutional monarchy, democracy, military dictatorship, foreign occupation and colonization - and failed in everything. According to the US ambassador of China, John Leighton Stuart, China regularly had 3 - 7 million people starve to death every year by that time.
What was China like at that time? It was a largely agrarian, backward, feudalistic, drug addicted, ignorant, and violent country with little or no industrialization. It had 400 million people, 50 million of them were drug addicts. 80% of the people were illiterate. The average life expectation was ~ 35 years. Poor people sold themselves into slavery on daily basis - it was either lifetime bondage or death by starvation. The Guangdong and Guangxi provinces, home town of Li Zongren, the vice president of the KMT government,are some of the wealthiest provinces nowadays with quality of life approaching developed countries, but back then Li wrote that everyone there was a drug addict, his own family included, and there was no hill in the country without bandits who waylaid travelers. The average rent paid by the peasants were 50% of their produce, and sometimes as high as 80% in Sichuan province near the capital. Women had their feet bound and lived a life more oppressed than that dictated by the Taliban. It was such a hell hole that the only thing separating the progressives from the conservatives in China was the degree of self-loathing.
Imagine a country a hundred times worse than Iraq, and you got China during WWII. In addition to 20 million soldiers and civilians slaughtered by the Japanese, 10 - 15 million Chinese starved to death within just three provinces in one year. Desperate mothers exchanged their children to eat. Chiang kai-chek wrote in his diary that when KMT army captured 1000 young men in one province to serve in the army, by the time they reached their destination only 100 of them survived.
By the 30's the Chinese were basically competing with each other to be the "good doggie" for the great powers. Wang Jingwei led the faction that went over to the Japanese. Despite the Japanese invasion, the Nanking Massacre, millions of Chinese supported the Japanese during WWII despite Japanese war crimes. Think about it - just how miserable their lives had to be before the Japanese invasion for these people to turn to the Japanese, the most brutal of all the occupying armies, for salvation?
Chiang Kai-chek converted to Christianity and handed a part of the Chinese military command to Joseph Stilwell, the American general. CCP handed its military command to Otto Braun (Li De), a German communist sent to China by the Soviets. Thanks to his incompetence, the CCP was the first to wake up and realized that they needed to figure out a path forward on their own, and not keep trying to be the "good doggie" of some other great power.