My understanding is that a President from founding until now has been afforded immunity from civil lawsuits for official duties, but it was never intended to shield a President against criminal prosecution. That is why Nixon stepped down, because he had crossed that line and was going to be criminally charged/prosecuted.
The court has now taken and re-written the law for Trump, knowing that Biden (or any Dem) President will not abuse this new King power that the Court put themselves in charge of determining what applies and what doesn’t. They have opened Pandora’s box thinking they can control this new power, but if a dictator wants to be a dictator, they will find a way around the Court. This is going to have long term major repercussions for generations.