If you were to have said Russia could grab Crimea and other parts of Ukraine without much of a peep 20 years ago ... nobody would have believed you. And then it happened.

China is on a path to grabbing Taiwan and they'll have enough power that they can just 'do it' - with sufficient political cover, it's possible.

March 21s, 2031:

CPP drives internal foment in Taiwan through years of placing and supporting agents, and use more radical pro-China antagonists of the 'New Taiwanese Patriotic Party' to divide the country, they challenge the results of an election (which was by all accounts fair) after a few riots (instigated), Taiwan could wake up to find 'little green men in unmarked uniforms' all over the country - the naval bases surrounded, Chinese jets completely swarming the skies displaying imminent air superiority, 5000 of these 'little green men' facilitate the pro-China Taiwanese political leader to capture the Premier and force him to concede. They ask the Taiwanese Army to stand down - some do, some don't. Some units are surrounded, unable to fight, some units stand down, a few firefights erupt but the unprepared units are quickly disposed of by the 'little green men' and their supporting forces.

Tanks of the 'New Taiwanese Patriotic Party Army' roll through the streets, some protests erupt like in Hong Kong. The 'New Premier' formally asks China for help to 'restore civility' and China lends thousands of police to help quash the uprisings. Thousands of people dissapear never to be seen again.

Some business leaders, paid off and sympathetic to China, call for calm and peace, trying to maintain some degree of civil order so that business can continue ...

10% of the population takes sides with the 'Patriotic Taiwanese Force' and their calls for Unification with China and act as informants, enforcers in the name of peace and stability.

The world protests and enacts some sanctions, but are unwilling to challenge China's position on the UN Security Council and so the reaction amounts to a few empty words. The world opts to keep the 'integrity' of the UN rather than dissolve over the Taiwan issue.

CCP publicly proclaims they are committed to the Sovereignty of Taiwan within a 'United China' and support the new revolutionary Premier and his 'transitional government'. A couple of years later, a new constitution is enacted which formalizes Taiwanese 'Unification' with China.

I don't understand why people think that something like this won't happen.

Stalin had full control over the Communist Party in Germany during the 1920's Weimar Republic, and he was constantly formenting dissent, used thugs in the streets, and ironically with the collaboration of the 'far right' (i.e. Hitler himself, who the Communists though were useful idiots) tried to overthrow the ruling Social Democrats. They were unable to do that, but we know who eventually did.

If the world wants to ensure the sovereignty of Taiwan it'll probably take some extra love and vigilance on that issue, with intelligence support for the government there, military aid, and maybe an unofficial Navy 'base' established by some semi-permanent presence. And possibly some other commitments by the world to raise the cost of invasion for China.

China has literally stated that this is their objective, they are pretty good at moving towards their commitments, and the world is an unstable place - a little bit of well place calamity is all it takes for some dominoes to fall.