I mean... I actually agree with (aspects of) that ruling. A nation's leader is going to have to, by necessity, do some really sketchy stuff. Simply put "war"
The issue is defining what counts as an "official act" and having any kind of checks and balances on that.
For example: Let's look at the purely hypothetical example of an outgoing president engaging in a violent insurrection against the US government in an attempt to prevent losing power. Crazy, right? But, in that example, it is not at all a stretch that said former president is an enemy of the state. There is a lot of legal discussion on whether it is legal to pop them in the head without a series of trials but it is in that range where it is probably better than not to give the elected POTUS immunity in that situation.
But what if that outgoing president insisted that it was an "official act" to lead that violent insurrection? No intelligent person would at all consider that a defense.
Whether described as presumptive or absolute,
under the majority’s rule, a President’s use of any official
power for any purpose, even the most corrupt, is immune
from prosecution. That is just as bad as it sounds, and it is
baseless
When the foremost observers of the fascist cabal say their ruling is "just as bad as it sounds", I will take their word for it.
Note that as bad as that is and as evil as it has sometimes been, it is "legal", and thus not subject to criminal prosecution. It is specifically legal for the president to do that sketchy stuff.
For an "official" act to be illegal, but not subject to prosecution just makes no sense. It shouldn't be possible for an illegal act to be "official".
Extra bonkers is the 5/4 opinion that you can't even mention official acts, like if you accept a bribe in exchange for an appointment, you can't mention the appointment while trying to prosecute the bribe.
Prior presidents have done all kinds of shady shit without worrying about prosecution. Even the angry orange didn't get charged until he tried to overthrow an election.
There was zero reason to even decide this case except to give immunity to someone who blatantly abuses their authority.