Backdoor ties to mitigate Brexit. As for the defense aspect, they already have a mutual defense pact…NATO. Unfortunately, we're in it too.
1.3 billions people. You have to keep them busy doing something. And with all of the money they have been getting from us via trade, they have it to spend. IMO.
Who knows. But you have to believe they don't need any more people there. Plus, they really don't like non-Han people, including other Chinese citizens.