The nationalist, is basically a dictatorship, and did not treat taiwan people well. (usa helped its suppression of dissents)
Dissents are put to death or jail. (most famous example is historian Li Ao, who got in jail for several years. (he died some 4 years ago))
There were also mass killings of taiwan people, the 228 incident, some 18k killed.
By the way, Taiwaness has many meanings.
It can mean the chinese living in taiwan before the nationalist came. (this is called “Taiwaness” in my generation.)
It can mean the nationalist who escaped to taiwan. (e.g. My parents)
We are called “foreign province people” (waishengren 外省人, aka mainlanders)
the distinction between Taiwaness (Originally in Taiwan) vs Mainlanders (Escaped to Taiwan), was the most important political distinction, in my generation.
Either way, we are all Han Chinese. 98% or such of people living in taiwan, are all Han Chinese.
It can also mean, aboriginals or natives taiwan (a western concept, e.g. redskin or the na'vi of Avatar movie), which are 0.01% or such.
For 30 years, us considered china 🇨🇳 belongs to ROC taiwan 🇹🇼 , till 1979.
(Mao created nukes in 1964.)
United Nations (UN) also began recognizing China at the time.
Chiang Kai-shek 蔣介石 (the leader of KMT), rage quit UN at the time.
Since y2k, taiwan gradually became multi-party. In particular, the Democratic Progressive Party (DPP) gained power.
(the DPP, and the KMT, are the 2 large fighting powers, very similar to us's Democratic Party vs Republican, in clawing each other's eyes out.)
The DPP, began good in 2000s, but today became extremely corrupt, lead by Tsai Ing-wen 蔡英文 (who, slaves on twitter posting in english singing “democracy” everyday. A pet of usa).