Why were Mao Zedong and the Chinese Communist Party able to gain control of China in the years 1937-49?

Mao Zedong and the Chinese Communist Party(CCP) were able to gain control because of many reasons. Almost all the Chinese people living under Chiang Kaishek's rule weren't happy because of high taxes, accusations and chaotic life. Many people under GuoMingDan(GMD) rule left to live under CCP rule where there were lower taxes. Peasants especially were attracted to CCP rule because the land was distributed fairly and people gave them self-respect. The red army …

…the GMD head-on. Also because the GMD was so weak by now, the American government stopped helping Chiang Kaishek in 1947. I think there were major problems facing GMD and tipped and favored the CCP. Overall I think the CCP were clever and were opportunists and took advantages of the GMD weaknesses and made the most of it. GMD lost all of it's strengths and lost support from workers and peasants, the majority of the population.