The offer is partly because of the threat to South Korea from North Korean missiles.
I am sure it is. It is also a way for the game between North and South Korea to D/C ( Destruct and Construct its OODA loop).
The North and South Korea have been gaming each other for years, and the players have the game pretty much in hand. But structuring a wall between the two, with the use of a missile defense, changes the game.
The front between the North and South is clearly defined, but this new structure Acts as a fog that covers the front, and makes the players Act differently.
Look for a whole new game to take place and billions of dollars flow into the region to upgrade the rule-sets. Look for the “reciprocal procurements” to add billions to the region’s economy.
All war is about economic considerations, and fought by people with little economic considerations.