Why?
First, there's plenty of money in he US and Europe. I feel they could have worked a bit harder to secure non-Chinese funding.
Second, like it or not the world is engaged in an economic war with China. The industrial bases in the US and Europe have been destroyed to the point that entrepreneurs have trouble finding such things as machines to sew socks. Issues abound across a myriad of industrial segments.
While some in the western world might be all hippie/feel-good about China this is at the cost of ignoring what has been going on. Before you call me a paranoid asshole consider I've been manufacturing products in the US for over thirty years. During that time I have seen, first hand, what the reality of manufacturing has become. Over the years I've seen vendor after vendor systematically taken out by China's expansion into every nook and cranny of industry, even in areas you'd think make no sense.
Now the Chinese are going to insert "probes" into thousands of startups by means of providing insignificant (to them) funding. This will give them unparalleled visibility into trends, products and whole new industries ripe for pillaging.
AngelList is a fantastic resource. I am sure they could have made an effort to source this fund in the US and Europe. In the grand scheme of things $400 million is not that much money with the clout AngelList has, particularly if spread across a range of investors. I, for one, would not want to have a Chinese investor.
Down-vote away.