As to the first question, why were the Communists so appealing compared to the nationalists,
1) the nationalists were obviously corrupt. Chiang Kai Shek was a political operative you gained power by making deals with various corrupt people.
2) the nationalists were seen as self-serving wimps. During World War II China was invaded by Japan. Chiang predicted that the US would kick the s*** out of Japan. He also predicted that after the war the Communists would attempt to rise to power. So he withheld forces and did not fight hard to kick the Japanese out of China , instead opting to wait for the u.s. to beat up Japan. In contrast, the Communists were fighting extremely hard against the Japanese to liberate China. Obviously the people of China saw the Communists as the more patriotic force.
3) The Communists had better public relations.