The ruling seems logical to me. Presidential immunity is restricted to conduct related to the nation's business and does not extend to a president's personal affairs.
Excerpts from the ruling's Opinion of the Court section:
Trump asserts a far broader immunity than the limited one we have recognized. He contends that the indictment must be dismissed because the Impeachment Judgment Clause requires that impeachment and Senate conviction precede a President’s criminal prosecution.
Historical evidence likewise lends little support to Trump’s position.
The implication of Trump’s theory is that a President who evades impeachment for one reason or another during his term in office can never be held accountable for his criminal acts in the ordinary course of law. So if a President manages to conceal certain crimes throughout his Presidency, or if Congress is unable to muster the political will to impeach the President for his crimes, then they must forever remain impervious to prosecution. Impeachment is a political process by which Congress can remove a President who has committed “Treason, Bribery, or other high Crimes and Misdemeanors.” Transforming that political process into a necessary step in the enforcement of criminal law finds little support in the text of the Constitution or the structure of our Government.
Trump v United States
Excerpts from the ruling's Opinion of the Court section:
Trump asserts a far broader immunity than the limited one we have recognized. He contends that the indictment must be dismissed because the Impeachment Judgment Clause requires that impeachment and Senate conviction precede a President’s criminal prosecution.
Historical evidence likewise lends little support to Trump’s position.
The implication of Trump’s theory is that a President who evades impeachment for one reason or another during his term in office can never be held accountable for his criminal acts in the ordinary course of law. So if a President manages to conceal certain crimes throughout his Presidency, or if Congress is unable to muster the political will to impeach the President for his crimes, then they must forever remain impervious to prosecution. Impeachment is a political process by which Congress can remove a President who has committed “Treason, Bribery, or other high Crimes and Misdemeanors.” Transforming that political process into a necessary step in the enforcement of criminal law finds little support in the text of the Constitution or the structure of our Government.
Trump v United States