China wants direct control over the chip fabrication capabilities of TSMC, which produces ~90% of microchip fabrication in the 5-10nm range and ~60% of all microchip fabrication. Exerting control over the rest of the world's access to advanced microchip fabrication is the primary goal. Don't pretend China's aggressive behavior is about anything else.

Taiwan and China are tightly integrated in terms of culture (the best selling artist in China is Taiwanese, for example), and bilateral migration between China and Taiwan is extremely high.

Less than 12% of Taiwanese citizens support unification with the PRC, while 50% support Taiwanese independence and 25% support maintaining the status quo (see section 10). Additionally, 62% support Taiwan seeking international recognition as a sovereign nation (section 6).

Meanwhile, Taiwan is literally a fortress with a massive force of military-trained personnel.

Of course it is, they are being threatened by an aggressive authoritarian nation with a vastly larger military.