This is a misleading partial quotation. In the context of what they were saying, the president has the presumption of immunity, but it is not guaranteed. They specifically remanded the issue of Trump trying to get Pence to break the law to the lower courts to decide whether there was immunity. They did not say there was blanket immunity.
The question then becomes whether that presumption of immunity is rebutted under the circumstances. It is the Government’s burden to rebut the presumption of immunity. The Court therefore remands to the District Court to assess in the first instance whether a prosecution involving Trump’s alleged attempts to influence the Vice President’s oversight of the certification proceeding would pose any dangers of in- trusion on the authority and functions of the Executive Branch.