Since decolonization was a global phenomenon, this question requires an answer that accounts for global and local causes. First, by the end of WWII, the colonial consensus had begun to collapse. State elites had begun to challenge the legitimacy of colonialism as a form of rule. Woodrow Wilson's 14 points, the Russian revolution, & the mandates after WWI had all introduced critiques of colonialism into the global system. You could see this building. During WWII, Queen Wilhelmina of the Netherlands (East Indes/Indonesia) and Free French leader Charles de Gaulle (Indochina) scramble to make pronouncements about the reform and liberalization of their empires, investing local populations with real power. These statements were aimed at the local population but also toward the United States, who they understood was opposed, especially under FDR, to the continuation of colonial rule.

Specific to the area, I would say that the mobilization of troops was perhaps the primary factor. First, Europe had mobilized men in the colonies to fight in both world wars. For Britain, India was an enormous force multiplier. In exchange for the mobilization of its men and material, Indian leaders struck a bargain with Britain for greater autonomy as WWII began. This agreement was the beginning of the end of British rule. During the war itself, the break in European rule was crucial. New armed forces sponsored by the Japanese like those of Subhas Chandra Bose, Aung San in Burma, or Indonesian troops under Sukarno, allowed for the development of new ideas, identities, and networks. In the French empire, for example, in the colonies that they retained control over during WWII, there was no serious revolt/revolution--only in those they had lost control over during the war.

The ROC did certainly assist. They had been harboring and assisting non-communist Vietnamese revolutionaries since the 1920s (they did not like the communists though for obvious reasons). And they did force France to sign an accord with the Democratic Republic of Vietnam gov. before they would allow them to return to northern Vietnam. That truce ended shortly after China ended it's post-war occupation of Vietnam though. The communist Vietnamese then cracked down on the nationalist Vietnamese parties, and France violated the accord in Dec 1946. So it was not a stunning success by any means. The two bigger factors were the growing de-legitimization of colonialism on a global scale and the mobilization of anti-colonial forces in the colonies during WWII.

As someone who is Taiwanese, I have to say that article sounds like self-aggrandizing propaganda. While I'm sure that Chiang Kai-shek may have stated that he felt strongly about independence for other Asian nations, he was getting beaten six ways to Sunday by Japan and the CCP and so wouldn't have much real influence on these movements.

If you want to look at actual reasons for decolonization in East and Southeast Asia, the reason is probably Japan. According to the US State department (https://history.state.gov/milestones/1945-1952/asia-and-africa), one of the reasons that Europe lost it's hold on Asia is that Japan kicked them out, and when Japan was forced out, all that was left were the nationalistic guerrilla forces trying to free their homes. This led to a temporary vacuum in which many nations were able to establish a strong enough foothold to take their independence from European powers, though this sometimes led to the rise of murderous dictatorships, and/or massive clusterf***s (technical term).