I don't know how much truth there is to this, but from the point of view of the several hundred Chinese netizens I know, a lot of China's current international policy decisions are arising out of desperation. For the past couple of decades, China has experience about 10% growth to its economy per year which has led to a wealth gap that makes ours look small. While the tide was rising, I suppose the average Chinese citizen had hope that perhaps he too can make it big... but with Xi's crack down on corruption (which, for good or evil, was just how business had worked in China), the economy slowed down considerably.

With that slow-down, the feeling of hope that the young unmarried men of China depended on to buoy up their spirits (it needed buoying up because there is tremendous societal pressure for them to find a good wife, but they outnumber girls their age by as many as 17 to 1 in certain cities) just vanished, leaving in its place restlessness and frustration. And if you get a bunch of young, restless, and frustrated men together, you have the historically tried and true recipe for destruction. I guess China's leadership, fearing for government stability, is looking to turn that sentiment outward via war, rather than take it inward via civil disobedience / revolution.