Specifically because China has now opportunity to gain international trust. Also, their own advancements in semiconductor manufacturing make Taiwan less attractive of an asset.
It has always been a legitimacy issue over who is the legitimate heir of the Chinese empire. China is still in a civil war. The communists (CCP) conquered the mainland and the former ruling party of China (KMT) fled to Taiwan. Taiwan is more successful than mainland China per capita on almost every standard economic and human development metric. It exists as a thorn in Beijing's side.
From the PRC perspective, reunification is a matter of national pride, and has nothing to do with semiconductors.