"a country that has explicitly set out to usurp the US is useful"
Can you provide some evidence for saying that China "explicitly" set out to do this? The Chinese government has been consistently "explicit" that it does not aim to replace or supplant the US [1][2][3]. Perhaps you mean "actions speak louder than words" and that this intention is evident from the actions they've undertaken, in which case it would be nice to know what actions you have in mind, as well as how you ruled out boring explanations of those actions that China's leaders would have given themselves.