They haven't crowned the POTUS as king. They were very clear that non-official acts are not covered. They've crowned themselves, the ones who get to determine what is and what is not an "official act" the kings.
Not that I would ever suggest it, but I bet the moment a president even attempted to abuse this official power against these six conservative traitors to democracy, they'd desperately try to walk this decision back - they only care for the potential of abuse when it negatively affects them
President Trump signed Executive Order 13823 which kept Gitmo open and declared that the USA can detain "persons captured in connection with an armed conflict for the duration of the conflict." That being stated in Trump's executive order makes it clear that detaining such a person would be an official act.
Trump and his MAGA supporters have made unproven claims that the 2020 election was stolen and they intended to overthrow the government and install him as President on Jan-6 despite his election loss. Trump and his supporters have made continuous threats of violence and committed numerous acts of violence since then. It is therefore clear that the violent conflict that started on Jan-6, 2021 has not yet concluded. Trump and members of his MAGA army can legally be detained, without charge, for the duration of this conflict if and when they are captured.
Now there may be some question about who would capture Trump and his criminal allies and where they would be detained. It's really quite simple. George W. Bush gave us extraordinary rendition. This program used agreements with about 50 other countries to abduct "terrorists" off the streets of those nations and hold and interrogate them indefinitely in CIA black sites. It is debatable on whether or not the CIA, NSA, or FBI could legally capture Trump or any of his terrorist allies, but that is not a problem. No doubt there are any number of foreign powers that would be happy to do so on our behalf for some diplomatic or financial consideration. Negotiating with other nations and arranging treaties and agreements is unarguably part of the Presidents job and therefore an official act.
Thanks to this ruling all Biden needs to do to save our democracy is to come to an agreement with one or more nations to capture the terrorist Trump and transport him to some black site in a foreign nation. There he can be held, and interrogated if need be, until such time as the conflict with his MAGA army is ended. If there are any legally questionable actions by Biden here, they in the nature of official acts, and he is therefore immune to prosecution now or in the future. Should anyone else involved be charged with a federal crime during the capture or detention, Biden can simply pardon them.
Thank you SCOTUS. You've given Biden the ability to save our nation with no legal risk to himself or anyone else involved in the process... Except, Biden would never do any of this because he is a decent human being. So what SCOTUS has really done is destroy our nation. This is the dumbest ruling ever made by this or any other SCOTUS in the history of this nation. The next Republican president will almost certainly not be a decent human being and will commit atrocities that he or she will never be prosecuted for and will tear down our democracy and will rebuild our nation as a Christian theocracy.
Considering that an ex-president who invaded a country under a proven false pretext and in violation of international law and has a million Iraqi civilians on his conscience is still painting his little pictures in Texas, perhaps the Supreme Court decision is not as big a break as some seem to think?
Why is there a picture of Trump?
He's not the president.
Edit:
Apparently some people just don't have the ability to pick up on the subtext that Trump isn't president at the moment and Biden could also use HIS shiny new presidential powers on Trump too.