As I understand it, he has the authority to fire for cause. There's just very dubious cause here -- like how he tested the waters with firing Powell over the cost of hq renovations after SCOTUS told him the Fed is different.
Notably in a lot of these cases they’re just canceling injunctions, not deciding the merits.
But effectively it decides the case because nobody is going to stick around through a long trial after the injunction is canceled.
Which basically makes The Supreme Courts shadow docket a fairly arbitrary justice system that doesn’t generate precedent and many courts ignore past the immediate case.