I thought that goes without saying:

• They already have connections in Taiwan, so that’s the easiest workforce for them to draw from.
• They have closer language & cultural ease with fellow Taiwanese people than people from anywhere else in the global labor market.

But this article isn’t about Taiwanese H1-B visa workers vs other H1-B workers, it’s about H1-B workers vs domestic workers. The fact that almost all those H1-B workers happen to be Taiwanese is a bit of a red herring.