Chinese Communist Party has tied it's legitimacy into uniting China. Xi has doubled down on it. Giving up would destabilize the party. It's and identity question for China. Chinese law ways that China must go to the war if peaceful unification is not possible.

Even Chinese people seem to think that Taiwanese want to be part of China. In reality support for unification is about 4% of the population. The official One China Policy exists to prevent immediate start of war.