The soviet union did not contest that order so much as exist outside of it. When it collapsed, those institutions didn't change they just lost their counterweight.

aggregate economic growth is positive sum, but the things that actually matter in geopolitics, namely who controls chokepoints, who sets standards, whose currency denominates trade, who has military primacy in a given region are zero-sum or close to it. china getting richer grows the pie. china getting rich enough to contest US naval dominance in the South China Sea does not. both are happening simultaneously. pointing at the first doesn't make the second disappear.