Arguably they would be in a safer position if they didn’t try to control those waters. A blockade would’ve stopped Chinese imports, yes, but it also would’ve stopped Chinese exports. And their exports play a significant role in the global economy and international trade. They really didn’t need to secure the area militarily because they had economically guaranteed a blockade would be broken.
This is pure speculation, but I think their belligerence may be what prevents them from rising to a superpower.