The Mahayana emphasis on helping others to find enlightenment, rather than the Theravada emphasis on personal salvation (in successive lifetimes) appealed to the Chinese interest in developing the community.
So the idea of the bodhisattva—the Buddha-to-be who has foregone enlightenment to help others reach it first—made sense to the Chinese. In Mahayana, the bodhisattva was the ideal person, while in Theravada the ideal person is an arhat (monk-like meditator).