So what? When it comes to fighting wars, economic connections don't mean much. Europe had enormous economic ties and traded with each other all the time; yet they fought each other all the time. We frequently use that argument and it ends up being wrong, especially since I see a looming trade war on the horizon.
When this breaks out, it's not going to be anything resembling a rational decision. China will consider an invasion on Taiwan to be a "defensive" military action, especially since they've got independence movement elsewhere, like Tibet, and let's not forget that their pride will be a big motivator as well. I don't expect nuclear weapons to be used right off the bat, but if they think they have no other choice, they will. They have repeatedly threatened us with nuclear war over Taiwan.
One of the biggest things to consider is self-delusion, which is a major part of any crisis war. Japan deluded themselves into thinking that they could launch a war against us and win. We deluded ourselves into thinking that nothing like that could ever happen. In our civil war, both sides believed it would be a quick struggle and they'd be back home by the time the leaves changed.