https://www.supremecourt.gov/opinions/23pdf/23-124_8nk0.pdf
Basically, the original judge did a good job - the settlement plan was reasonable and widely popular. And the Sackler family being released from liability by putting billions of personal dollars into the payment fund meant more victims would get more money immediately.
With this ruling, the Sacklers are personally legally liable again - which may make you or I more happy, but this means that victims have to pursue a much harder and more expensive set of lawsuits to get money from the Sackler family. It also means the victims of the deal don't get a voice in the proceedings, and it may also make future payouts and bankruptcies harder if there is no reason to cooperate with the state.