His goal was to not play into the hands of the media. They were ready to run constant coverage of violence in the streets and attribute it all to Trump because muh peaceful protesters clashing with riot police. Instead he offered help, and then let the governors deny him then let their own cities burn. As far as optics go, that was the winning move by not playing into the media's ploy. It wasn't pleasant, but those events alone were enough to sway some opinions in his favor. If his help had been accepted, like in Wisconsin, the problem was solved quickly. Showing his strength when they cooperate.