The most important thing is that Xi convinced Trump about the position of Taiwan for the USA and China. You may say that this is brainwashing. The key is that the brainwashing must be acceptable. Both leaders must have discussed something and reached mutual understanding of the current world situations. That is why face-to-face close door meeting is very important between superpower leader to avoid misunderstanding and guessing. They do not talk to each other like talking in the public.