The DC indictment is structured in such a way as to demonstrate that Trump was way outside his duties in committing election fraud, so I think the majority of the case is safe in-theory. But we are continuing to backslide and this is up there for worst SCOTUS decisions in our lifetimes.
But they generally see themselves as the arbiters of all that could be ambiguous. This seems like a very classic fashy move to give a semblance of legality & rationality. Gives themselves a tool to decide DT actions were technically official while Biden actions in a hypothetical indictment won’t be.
People will continue to harp on Merrick Garland (which fair, he has sucked) but this ruling has me pretty certain that no matter how quickly he worked we were never going to see a federal case against Trump go to trial