I understand what you are saying, but if Trump does that, he will be accused of being a dictator, which is why he allowed the governors to do their own things.
If Trump declares this “emergency” over, they will have no excuse for their un-Constitutional acts and ruling by edict, which probably is not even permitted in their state consitutions.
Federalism is one thing, but virtual secession, with the states each going their own way, even in violation of the Constitution, is another. The only reason they’re not seceding outright is that they want to keep Federal money flowing. And that’s something else he can do: cut off the money.
Hopefully, he won’t give them any money for rebuilding the cities that they allowed to be destroyed by permitting these riots, and he shouldn’t give money to states that won’t open up and let their economies start moving again. This will certainly also result in a lot of popular pressure on the governors to quit playing politics and open their states again. And to mayors, as well, because some of them are feeling so empowered by this “state of emergency” that they are defying more open state policies and issuing paralyzing edicts for their cities. If there’s no more emergency, there’s no more “emergency powers” like this.