DeSantis Isn't Violating Federal Supremacy
His Mandate Ban Is Consistent with the Court's Ruling
DeSantis' action does not violate the Supremacy clause: The Federal Government is not ordering hospital staff to be vaccinated but making it a condition of continuing to receive Medicare funds. So the governor is insisting they act in such a way that they can no longer receive those funds. Where is he defying Federal authority? He may be defying Federal intent, but he is not actually violating Federal law in any way or refusing to obey the SCOTUS---unlike DC which circumvented the Heller decisions intent in a way that was likely illegal.
The Federal government decided to word the law using a carrot/withdrawal of the carrot approach. There are consequences to using such indirect methods though direct methods may not be Constitutional; that is always the risk.