Somehow a very important piece of information has been deliberately overlooked.  
That is the Hong Kong independence movement.  often reported in the South China Morning Post, which covers the riots and the protests.    
Taiwan could be considered a "province" but operates freely with independence and apparent co-operation with China. The history of Taiwan is well covered in , The Soong Dynasty" by Sterling Seagrave.
The S.C. Post also states the the president, Tsai Ing-Wen initiated the phone call. 
Hard to believe but Trump did the right thing.