There are probably arguments to be made about the communists' work to help peasants during and after, but I'm not too knowledgeable on that. What I can tell you, is that prior to the Japanese invasion, the communist army was pretty close to being eradicated.Mao and his army had just finished their long march, and were down to about 10% of their original size. Even after the Japanese invasion, Chiang Kai Shek still wanted to focus on defeating the communists before he was forced to form a united front with them against Japan. If the Japanese had not invaded when they did, it is likely that the Nationalists would have eradicated the Communist army. So in a sense, yes it did help Mao rise to power as he probably wouldn't have had the chance without the Japanese invasion.