https://en.wikipedia.org/wiki/Trump_v._United_States
On July 1, 2024, the Court ruled in a 6–3 decision that presidents have absolute immunity for acts committed as president within their core constitutional purview, at least presumptive immunity for official acts within the outer perimeter of their official responsibility, and no immunity for unofficial acts.[5][6][7][8] The court declined to rule on the scope of immunity for some acts alleged of Trump in his indictment, instead vacating the appellate decision and remanding the case to the district court for further proceedings.
Since 2024, SCOTUS has sided with Trump about 90% of the time, so most likely it's legal.
Still, even if it's later determined to be illegal, since the law presumes the president has legal immunity to all crimes committed in a presidential capacity, there's no legal risk, so the damage can be done long before the court makes it illegal. For example, Trump's global tarrifs were determined to be illegal a year after the fact, long after the damage had been done.
Their inability to find a backbone helps them contort to whatever Trump babbles that day, even if privately they know something is idiotic or illegal.
If you want a prime example, look at how Thom Tillis suddenly finds the ability to speak out once he lost his primary.
What it would do is have an instant chilling effect across Corporate America, which is the goal.