The same reason they are being "shut down" everywhere. Other countries are also shedding manufacturing jobs as technology increases the productivity of each labor hour.
Smoking pot? So if a factory in China automates what was the propose of offshoring? Wouldn't that same factory be just as profitable in the USA? With no labor costs( assuming 100% automation) then the offshoring meme gets a little stale. You are are what Marx called one of his useful idiots.
George Washingtonian was a protectionist. So was he misguided? The issues of trade are the same as they have always been.