Your article does not say that China was producing such massive quantities of CFCs that the efforts of all other signatories to the treaty were negated. What your article does say:
> Scientists largely credit the Montreal Protocol, signed by about 150 countries, with reversing the depletion of the ozone layer
This graph shows that in 1997, reductions in CFC had just begun, yet the ozone hole had been reversed.[1]
Also, apparently there isn't agreement that the hole has gotten better: "Work has suggested that a detectable (and statistically significant) recovery will not occur until around 2024, with ozone levels recovering to 1980 levels by around 2068."
> Scientists largely credit the Montreal Protocol, signed by about 150 countries, with reversing the depletion of the ozone layer