There is absolutely zero evidence that any of his actions will result in any jail time. There is evidence on the contrary though, that through 2 impeachments, however many court cases and legal battles, fines and fees that may not have been paid, that he’ll get away with it all.
It was just common because no president wanted themselves in a position of fighting court battles for poor decisions they made in office. Of course this set the standard both ways, by letting both bad decisions made by good and ill intent slide.
And then the supreme court wanted to make it clear by setting it in ink that it’s ok.