The corruption accusation is a common playbook of Communists around the world, like in China, Vietnam, Korea, etc. All the power establishment were accused of being corrupt. The matter of fact is that in those countries, the power has always being deeply corrupt, because they never had a constitutional republic / democracy, which are later western inventions.
So in China, the National Party was corrupt, but not really that corrupt in the context of China's history. But surely very corrupt compared to western countries. Asking China to have a clean government at the time is like asking China to develop a moon landing project at the time. Communists of course understood these but they heavily targeted the U.S. government to spread the corrupt accusations. For example: "1944年6月罗斯福派副总统华莱士访华,冀全程陪同,提供了蒋、孔家族贪污腐败情况。"[1] 冀朝鼎(Ji Chaoding) was a CCP spy.
The whole "poor was hopeless and the elite class also distrusted the government" was Communists' propaganda too.
Remember, even though Communists at the time claimed they support democracy, but none of the Communist countries even attempted to establish democracy after they took power. All straight went to authoritarian hell.
[1] https://zh.wikipedia.org/wiki/冀朝鼎
[2] https://en.wikipedia.org/wiki/Ji_Chaoding