It comes down to states rights, and government that is part federal and part state.
The Governors have inherent police power in their own states.
Trump CAN help IF THEY ASK FOR HELP.
If they do not ask for help, and do not want Trump to just “go in”, he is acting beyond his authority unless there is a MAJOR disaster, or TOTAL loss of civil order.
Trump is pugnacious, and likes to bring global attention to his exercise of his Presidential Power.
SCOTUS will not go along.
Six of them are conservatives like me.
Since 1985 I have been in the Bar of that Court.