Whatever "a lot" means . . .
We had a war in Europe and a war in the Pacific. He may have been a bit busy to mess with small potatoes.
The why for the declarations could be gleaned from a comedy film put out just a few years after VE Day. "The Mouse that Roared." A small, dying country declares war upon the dominant nation of the world, hopefully a nation that will adhere to international law, has a single skirmish, and hastily submits to the mightier nation's obvious victory. Now come recompense for war damages and aid for nation-building.
What would you expect from a monarchy?