It is not a physical Taiwan invasion they fear.
It is that desire for Taiwan freedoms and living standards might become contagious.
Sure, China has prosperous citizens, but they also still have abject poverty in many rural areas.
They are terrified of losing absolute control of the populace.
Aren't most dictators scared of that?
A little historical context seems in order here.
It is true China cannot move it’s armor and infantry into Taiwan without massive Chinese Politburo destabilization level CCP/PLA losses.
But how Taiwan get to this level?
In a generalized nutshell —
Historically, the idea of the CCP involved the Communist Internationale and the global communist takeover goal and governance of the Supreme Soviet in Moscow.
In 1921, Vladimir Lenin hand picked Mao Zadong to support and lead a communist revolution through China, but also with the goal of spreading communist revolution throughout all of Southeast Asia.
In at least one twisted sense, WWII was an bloody interruption to an already super bloodbath under way. Without going into the weeds more on China, let’s just say it was a horrific bloody mess.
Toward Taiwan (Formosa), and what it means today
Taiwan has been building and maintaining a coastal super fortress since 1948/1949 when Chiang Kai-shek (the leader of thr Republic of China) KMT forces and Mao Zedong’s Moscow backed Communist CCP entered their final battles.
A 300,000 Chiang Kai-shek KMT force was airlifted to Formosa (Taiwan), as Mao’s CCP forces (backed by Moscow), absolutely crushed the Chinese people.
Eventually, (depending on the author), Mao’s CCP forces and policies would be responsible for the deaths of roughly 80 to over 100 Million Chinese people. Millions of Chinese people fled for their lives, and desperately tried to float to Formosa (Taiwan) to escape Mao’s hell bent blood drenched Communist army.
Today —
As Taiwan is nothing less than a super fortress, a modern CCP blockade and missile strike strategy are CCP’s only real immediate options, unless CCP Chairman Xi wants to (arguably) lose an estimated 1.5 to 1.7 million CCP PLA troops in an effort to invade Taiwan.
What Taiwan is actually facing —
China is geographically roughly the same size as the US, with either the 1st or near 1nd largest population in the world, with the world’s largest standing army.
As well, China is formally the 3rd largest nuclear weapons power in the world, and is believed to possess the 2nd largest chemical weapons stockpile.
As well, Taiwan does not possess nuclear weapons, and really only has a small c ok at guard type model navy.
Taiwan has remained in a very vulnerable and dangerous sphere since 1949.