HSBC founded in Shanghai before the communists took over and then prospered in Hong Kong moved its HQ to London some years back. Now its CEO is moving back to Hong Kong effectively moving the HQ back. Headquarters is where the chief works even though technically Hong Kong is just a branch unlike the past before HQ was moved to London.
Familiarity with the region has nothing to do with this move. Yes, growth in China is a major factor. What is significant is the de factor affirmation at the highest echelons of the bank that the global center of gravity in global economy has shifted to Asia, especially to China, and most likely for a very long time to come.
The full story is here.