Their problem is no one wants Yuan. To have a global currency, a country must allow free trading of the currency, it must have banks that appear solvent, and it can’t have a currency connected to domestic politics.
And no one with a lick of sense trusts China to keep honest account books as to its currency or public or company finances. Buying Chinese goods is one thing, but buying Chinese assets is subject to the political and economic risks inherent in a Communist regime.