Uphold the feudal social contract. Daeron II kept the Iron Throne entirely because his bannermen stepped up and held the line even when the Hand and the King himself (if we’re being honest) were completely ineffectual.
Especially when you’re in the opening stages of a multi-generational civil war and you’ve just gone from Valarr to Aerys as your figurehead, you need to reward that loyalty because it’s what’s going to win you the war in the long-run.
So the King needs to be seen to be actively protecting his people, whether that’s in relief of the Great Spring Sickness and the drought, or in using at least part of the royal navy along with the Oldtown fleet to crush Dagon Greyjoy like a bug.
I would argue that the Third Blackfyre Rebellion could have been made a lot more like the Fourth if they’d done that…